Environmental Geology and Sustainability of Deltas
Summary and Keywords
Deltas have played a significant role in the growth of human civilization because of their unique economic and ecological importance. However, deltas are becoming increasingly vulnerable because of the impact of intensive human developmental activities, high population and urban growth, subsidence, climate change, and the associated rise in sea level. The trapping of sediments by dams is another major threat to the long-term stability and sustainability of deltas. The emergence and global acceptance of the concept of sustainable development in the 1980s led to the advent of several multidisciplinary and applied fields of research, including environmental science, environmental geology, and sustainability science. Environmental geology focuses on the application of geologic knowledge and principles to broad-ranging environmental and socioeconomic issues, including the specific problems confronting deltas. The key environmental geologic challenges in deltas (especially urban delta areas) are: increasing exposure and vulnerability to geologic hazards (flooding, cyclones, etc.), rise in sea level, decreasing sediment load supply, contamination of soil and water resources, provision of adequate drinking water, and safe waste disposal. The application of geologic knowledge and principles to these challenges requires consideration of the critical geologic controls, such as the geological history, stratigraphy, depositional environment, and the properties of the alluvial sediments. Until recently, most of the traditional engineered solutions in the management of deltas were designed to keep out water (fighting nature), typically without adequate geological/hydrological input, rather than building with nature. Recent innovative approaches to delta management involve a paradigm shift from the traditional approach to a more integrated, holistic, adaptive, and ecologically based philosophy that incorporates some critical geological and hydrological perspectives, for instance, widening and deepening rivers and flood plains as well as constructing secondary channels (i.e., making more room for water). A key challenge, however, is the establishment of a close and functional communication between environmental geologists and all other stakeholders involved in delta management. In addition, there is growing global consensus regarding the need for international cooperation that cuts across disciplines, sectors, and regions in addressing the challenges facing deltas. Integrating good policy and governance is also essential.
River deltas have continually played a significant role in the origin and growth of human civilization because of their economic and ecological importance, which makes them attractive for human habitation. Globally, deltas and associated coastal regions are becoming increasingly vulnerable and unsustainable because of the current unprecedented changes in the environment (e.g., high population growth and urbanization, climate-related changes, etc.) and the geographic locations of deltas in fragile low-lying coastal regions (Intergovernmental Panel on Climate Change, 2007). This article begins with an overview of the emergence of environmental geology, environmental science, and sustainability science, followed by a review of the major challenges facing deltas worldwide, with additional information on the Niger Delta as an example of a delta in a developing country. This is followed by a brief discussion, and the article concludes with a summary of contemporary delta management approaches and the need for adequate environmental geologic input, international cooperation, and good policy/governance.
The report of the United Nations World Commission on Environment and Development (WCED, 1987) formally introduced the concept of sustainable development, which stipulates economic and social development without irreversible damage to the Earth’s natural environment and the depletion of nonrenewable resources. The flexibility of the definition makes room for different disciplines to develop feasible solutions that can be communicated across various disciplines (Daly, 1990), with the ultimate goal of obtaining a solution that is acceptable environmentally, economically, and socially. The Earth Summit that followed in 1992 in Rio de Janeiro, Brazil, adopted a detailed global plan of action (Agenda 21) and commitment of member nations to economic development and human growth without destroying the life-support systems of the planet.
The Earth’s systems have changed more rapidly in the past 60 years than any other times in recorded human history (Da Cunha, 2014). Geoscientists have a new and critical role to play in this current dispensation. Superimposed on their traditional role in the earth-resource sector is the new role of applying geological knowledge and skills to broad-ranging environmental and socioeconomic issues that require integrated earth-science knowledge. This made it imperative for a paradigm shift from the traditional study of planet Earth and its processes as isolated, discrete components to the concept of an integrated whole-system approach (Earth system science). The concept emphasizes interactions and linkages, rather than components, and trends rather than specific contents (Alcamo, 2015; Eyles, 1994). The recent emergence of environmental geology is consistent with this paradigm shift. Environmental geology encompasses a wide range of geoscientific fields that include interactions between the Earth’s four components (geosphere, hydrosphere, atmosphere, and biosphere) as well as the activities of humankind and their impacts on the Earth’s natural systems (Montgomery, 1994).
Although deltas cover only about 1% to 2% of the Earth’s surface, their estimated total human population is about 10% of the world population, and their average population density is about 10 times that of the world average. Furthermore, some of the world’s large urban cities (Shanghai, Bangkok, Dhaka, Cairo, New Orleans, etc.) are located in deltas (Overeen & Syvitski, 2009; Syvitski, 2016). Deltas are the only landforms on planet Earth where human populations and socioeconomic infrastructures are faced with water-related hazards (especially floods). They are “hot spots” or “frontlines” of vulnerability and change and therefore constitute perfect laboratories for global sustainability efforts (Foufoula-Georgiou, 2013). The reasons for the unique position of deltas in the global sustainability agenda are summarized in Table 1.
Table 1. Ten Reasons Why Deltas Are Perfect Showcases for a Global Sustainability Effort
Hot spots of change
Deltas are sensors of upstream, downstream, and local changes.
Hot spots of life
Deltas have ten times the global average population density as well as unique biodiversity and culture.
Hot spots of economy
Deltas are centers of resource exploration and commerce.
Hot spots of food security
Deltas provide rich agricultural and fishery resources.
The perfect global story
All countries cherish their unique deltas.
Convergence of disciplines
Deltas require interdisciplinary research for a holistic understanding.
Showcases of high-impact research
Deltas inspire solution-driven, actionable research.
Deltas bring together research communities, regulators, businesses, and citizens.
Shared concern, shared resources
Collaborative efforts can provide a global depository of delta data, research, and progressive monitoring.
Engage and educate
Deltas are a perfect platform to increase awareness of global environmental change while teaching the next generation to “think globally.”
Source: Modified from Efi-Foufoula-Georgiou (2013).
The Emergence of Environmental Science, Environmental Geology, and Sustainability Science
Global environmental concerns emerged in the late 1960s because of the great difficulties in meeting the needs of the rapidly increasing human population and the corresponding increasing demands on the finite and depleting resources of the Earth. Environmental science, environmental geology, and sustainability science have central roles to play in the formulation and implementation of appropriate sustainable solutions to global problems, including those confronting deltas. These three disciplines show considerable congruence (Figure 1). For example, they (a) focus on the understanding of Earth systems (past, present, and future) and (b) utilize multidisciplinary and interdisciplinary approaches.
There is no universally accepted definition of environmental science. However, it can simply be defined as the integrated study of the biological and physical natural environment (plants, animals, soils/rocks, air, water) as well as the sociopolitical organizations, institutions, and structures created by humankind using science and technology. In other words, it is an interdisciplinary study of how humankind affects other living and nonliving physical systems of the Earth’s environment. A relatively new and highly multidisciplinary, inclusive, and holistic field, environmental science is an applied science that incorporates knowledge from all disciplines (biological, physical, and social sciences) to address environmental issues. It gained prominence as an applied science discipline in the 1970s because of the increasing public awareness of definite actions needed to address environmental problems and the need to use a multidisciplinary approach in analyzing complex environmental problems. Some of the publications and events that spurred the rapid growth of environmental science in the United States include the following:
• Rachel Carson’s landmark environmental book Silent Spring was published in 1962. The book challenged the misuse of pesticides by agricultural scientists and governments.
• The Santa Barbara oil spill occurred on January 28, 1969, as a result of a blowout of a well located off the coast of Central California near Santa Barbara. About 200,000 gallons of oil spilled over eleven days, and additional leaks resulted in the release of over 3 million gallons of oil into the seabed. The devastating impact of the spill had a powerful influence on public awareness, which spurred Congress to pass the National Environmental Policy Act at the end of 1969.
• In 1970, the first ever Earth Day celebration was observed. The same year, the Environmental Protection Agency (EPA) was formed.
• An oil slick on the Cuyahoga River, in Cleveland, Ohio, which was highly polluted from decades of industrial waste accumulation, caught fire in June 1969, causing extensive damages and huge public protests. The incident made Cleveland a symbol of environmental degradation. The resultant environmental advocacy played a major role in the passage of the Federal Clean Water Act of 1972.
The term sustainable development was formally introduced in 1987 in a report of the United Nations World Commission on Environment and Development (WCED). The report, commonly referred to as the Brundtland Report, is titled “Our Common Future.” The report defines sustainable development as “Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” It contains two key concepts:
• The concept of needs—in particular, the essential needs of the world’s poor, to which overriding priority should be given
• The idea of limitations imposed by the state of technology and the social organization on the environment’s ability to meet present and future needs (Oslen et al., 2006).
The concept of sustainable development has experienced huge success since its introduction, and it now pervades the agendas of most governments and corporations as well as educational and research programs worldwide.
The term sustainability describes a state of possessing capacity to continue indefinitely and implies long-term health of the global ecosystem for both present and future generations. Sustainability generally includes a balance of environmental, social, and economic issues. Sustainable development is the process of development from our present state toward the ideal state of sustainability. It is a process of enhancing the human socioeconomic and ecological well-being currently threatened by human practices that tend to pollute the environment. Sustainability is the destination of the process of sustainable development.
The term sustainability is widely used in environmental science, especially in terms of natural resources. According to Botkin and Keller (2003), sustainability has two scientific meanings: (a) Sustainable resource harvest means that the same quantity of resource can be harvested annually, and (b) A sustainable ecosystem is an ecosystem from which a resource can be harvested and the ecosystem is still able to maintain its essential functions and properties. Okiwelu and Noutcha (2016) suggested that sustainability is one of three predominant themes in environmental science; the other two are human population and global warming.
The term sustainability science was formally introduced as the name of a new academic field in 2001 at the World Congress in Amsterdam, “Challenges of a Changing Earth 2001,” jointly organized by the International Council for Science (ICSU), the International Geosphere-Biosphere Program (IGBP), the International Human Dimensions Program on Global Environmental Change, and the World Climate Research Program (WCRP). It is an interdisciplinary approach for achieving a truly sustainable global society by integrating all disciplines and policy. The website of the Proceedings of the National Academy of Sciences of the United States of America (PNAS) defined sustainability science as:
An emerging field of research dealing with the interactions between natural and social systems, and with how those interactions affect the challenge of sustainability: meeting the needs of present and future generations while substantially reducing poverty and conserving the planet’s life support systems.
Kates et al. (2001, 2005) asserted that sustainability science has strong roots in the environmental aspects of the sustainability concept, while Schweizer-Ries and Perkins (2012) referred to the discipline as “action research,” which combines scientific knowledge production and societal action for change. According to Battencourt and Kaur (2011), the major constraints to the application of sustainability science are:
• Its global mandate, which requires collaboration between developed and developing societies
• Integration of all disciplines (theoretical and applied)
• Bridging the divide between theory, practice, policy, and governance.
There is no doubt, however, that the emergence of sustainability science has given rise to extensive scientific collaboration globally.
Although there is considerable overlap between environmental science and sustainability science, the two disciplines differ significantly in their primary objectives. The primary objective of environmental science is to address environmental issues caused by human activities, while the primary objective of sustainability science is to attain a sustainable global society by responding to the challenges and opportunities of sustainable development through the integration of theory, science, and policy.
The onset of the Industrial Revolution around 1760 led to extensive excavation (mainly associated with mineral mining) and construction of large civil engineering structures (such as dams, power plants, etc.). However, the danger to the Earth and its environment as a result of increased industrialization, urbanization, and gluttonous exploitation of resources was only realized in the 20th century. The issue attained global priority attention, with emphasis on the need for environmental protection and restoration, toward the end of the 20th century, which resulted in two major world conferences, the World Conference on Environment and Development in 1978 and the Earth Summit in 1992.
Geology, the study of the Earth, became recognized as a branch of the physical sciences in 1786. James Hutton (1726–1797) originated the theory of uniformitarianism, one of the major fundamental principles of geology. The principle explains the features of the Earth’s crust by means of natural processes that occurred over geologic time. Hutton’s work led to the establishment of geology as a recognized scientific discipline and hence he is often referred to as the “father of geology”. Environmental geology is a relatively new subdiscipline that was not an integral part of traditional textbooks or curricula of geology. Other subdisciplines within this so-called “non-traditional geology” include engineering geology, forensic geology, medical geology, geoindicators, etc. Like any evolving specialty, environmental geology experienced initial recognition problems and was regarded as part of engineering geology for several years. The first set of publications on environmental geology appeared in the 1960s and the subdiscipline attained formal recognition as a separate specialty, different from engineering geology, in the 1970s.
Environmental geology relates directly to human activities, especially their impact on natural systems. The importance of geology to environmental issues was recognized quite early in human history, with the first landmark publication by George Perkins Marsh, titled Man and Nature, in 1864. However, environmental geology became widely known and accepted only in the 1980s. The American Geological Institute defined environmental geology as:
Application of geologic principles and knowledge to problems caused by man’s occupancy and exploitation of the physical environment. It involves problems concerned with construction of building and transportation facilities, safe disposal of liquid and solid wastes, management of water resources, evaluation and mapping of rocks and mineral resources, and long-range physical planning and the development of the most efficient and beneficial use of the land.
(Bates & Jackson, 1987)
Although the definition has remained essentially the same, there is increasing emphasis on hazard mitigation and environmental restoration in the practice of the profession. According to Hasan (1993), the overarching goal of environmental geology is hazard minimization and resource-use optimization.
There is a delicate reciprocal balance between human society and environment. Human activities tend to affect and degrade the environment and alter the land–water ecosystem, while environmental degradation results in economic and health losses. (The alteration of the land–water ecosystem is a unique problem in deltas more than in any other landscape.) The proper use of geologic principles and engineering practices can minimize both environmental degradation and economic losses. There are more publications on the origin and growth of environmental geology as an academic discipline in the United States than in any other region of the world. Some of the major events, regulations, acts, laws, and publications that contributed to the emergence of environmental geology in the United States are:
Formation of U.S. Environmental Protection Agency (EPA)
First textbook on environmental geology (Flawn, 1970)
Enactment of Safe Drinking Water Act (SDWA); amended by the U. S. Congress in 1986 & 1996
Enactment of Resource Conservation and Recovery Act (RCRA) by U. S. Congress
Beliot College, Beliot, Wisconsin, and Western Washington University at Bellingham commenced Bachelor of Science degree programs in environmental geology
Introduction of Master of Science degree program in urban environmental management at the University of Missouri
The U.S. Congress enacted the Comprehensive Environmental Response Compensation and Liability Act (CERCLA)
Subtitle 1 for CERCLA concerned threat to groundwater quality from leaking storage tanks
Another amendment of Subtitle 1 to create Leakage Underground Storage Tank (LUST) Trust Fund
Eight additional U.S. universities offered Bachelor of Science degrees in environmental geology
Nineteen U.S. universities offered Bachelor of Science degrees in environmental geology
The acts and regulations listed made it imperative for private companies and public agencies to engage experienced geologists to identify the presence and movement of contaminants in the subsurface. This marked the beginning of environmental geology as a profession.
The initial application of environmental geology in the late 1960s was in land-use planning and resource management, as demonstrated by the title of the first textbook on the subject, by Peter Flawn, Environmental Geology: Conservation, Land-Use Planning and Resource Management (1970). Other landmark publications include the works of Marsh (1864), Osborn (1948), Dasmann (1959), Betz (1975), Coates (1981), Montgomery (1994), and Turk and Thompson (1995). Currently, in the early 21st century, there are staggering numbers of publications in environmental geology, including textbooks, journals, magazines, proceedings (of conferences, symposia, and workshops), government and agency reports, etc.
The increasing prominence of the discipline prompted several journals to change their names. For example, the Bulletin of the Association of Engineering Geologists (first published in 1964) changed its name to the Bulletin of Engineering and Environmental Geosciences in 1995, while the Bulletin of the International Association of Engineering Geology became known as the Bulletin of the International Association of Engineering Geology and the Environment in 1990. In the United States, the discipline achieved academic recognition by the 1970s, and by 1993, environmental geology was offered as a BSc degree program in eight colleges and universities in the United States. This number increased by 233% within three years (Hasan, 1996). Outside the United States, environmental geology is generally offered as a postgraduate degree program.
Initially, engineering geology and environmental geology were regarded as the same discipline (Ivey, 1975). The very close connection between engineering geology and environmental geology is clearly demonstrated in the definition of engineering geology in the status of the International Association of Engineering Geology and the Environment:
Engineering Geology is the science devoted to the investigation, study and solution of engineering and environmental problems which may arise as the result of the interaction geology and the works or activities of man, as well as the prediction and development of measures for the prevention or remediation of geological hazards.
(IAEGE Status, 1992)
However, Hasan (1993, 1996, 2002) and other researchers regarded both as separate disciplines, a position that is still held currently by the majority of geoscientists in the discipline. In addition to all the topics covered in engineering geology, environmental geology also covers waste disposal, land-use planning, environmental health, pollution prevention, and environmental law.
Deltas as Hot Spots of Development and Global Change
Research on Deltas
Deltas are fragile, geomorphic complex systems formed where rivers discharge into a body of water, such as a lake, estuary, lagoon, sea, or open ocean. They are therefore the end products of both catchment and coastal processes. The term delta (from the Greek letter—∆—delta) was introduced by the Greek historian Herodotus in the 5th century BC to describe the triangular lowlands between the two main tributaries of the River Nile, in Egypt. In 1832, Charles Lyell defined the term delta (in his textbook, Principles of Geology) as “an alluvial land formed by a river at its mouth, without reference to its precise shape.” This was followed by the first comprehensive review of the several processes affecting the form, structure, and evolution of modern deltas written by G. R. Credner in 1878. Other landmark publications on deltas include those of Gilbert (1885), Fisk et al. (1954), and Coleman and Wright (1975), among others.
In the 1980s, research on deltas advanced from the development of depositional models controlled mainly by variations in sediment supply to sequence stratigraphic interpretations of deltaic evolution through multiple sea-level cycles (e.g., Van Wagoner et al., 1988). The historical stages in deltaic research can be found in several other comprehensive volumes—Morgan (1970), Broussard (1975), Oti and Postma (1995), and Giosan and Bhattacharya (2005). More recent research on modern deltas is driven by concerns about human influences on the river catchment, either directly through construction of dams and water consumption, or indirectly due to climate change. The current large number of publications on deltas is attributed to their important role in human socioeconomic development history and the ever-increasing unique challenges threatening the long-term physical stability and existence of deltas (Foufoula-Georgiou, 2013; Syvitski, 2008; Syvitski et al., 2009).
A report on the state-of-the-art understanding of the changes and vulnerability of delta systems (Overeen & Syvitski, 2009) jointly commissioned by the Land-Ocean Interactions in the Coastal Zone Project (LOICZ), the Global Water Systems Project (GWSP), and the Community Surface Dynamics Modeling System (CSDMS), discussed the changes and vulnerability of world deltas due to:
• Anthropogenic alteration of upstream freshwater and sediment inflows
• Anthropogenic alteration of sediment and water routing through deltas
• Hydrocarbon and groundwater extraction from deltas
• Sea-level change
• Increased frequency of extreme climate events.
The report recommended “a multi-disciplinary, problem-driven approach with experts from the fields of engineering, ecology, geography and human dimensions.” The report also added that a “large integrated community effort is sought to bring intellectual resources to address the problems of deltas.”
Economic and Ecological Importance
Globally, deltas are known for their great economic and environmental importance. They are strategically located close to seas and waterways and are endowed with abundant fertile agricultural lands, huge reserves of minerals, oil, gas, water resources, biodiversity, and other natural resources. Consequently, deltas have always attracted people since the beginning of human civilizations, making them hot spots of intense socioeconomic activities, fast-growing human populations, and ever-increasing human-induced environmental impacts. Deltas are highly widespread globally; 21 of the world’s 25 largest rivers have well-developed deltas, and deltas are responsible for up to 31% of the total fluvial sediment entering the oceans (Meade, 1996).
The following statistics and features of deltas obtained from various sources demonstrate their socioeconomic importance:
• About 25% of the world’s population lives within deltaic and wetland coastal systems. The population percentage is projected to reach about 70% by 2050 (CAETS, 2008).
• In 2000, the average population density in deltas was about 500/km2, compared to the world average population density of about 45/km2 and the United States’ average of 31/km2 (Overeen & Syvitski, 2009).
• The population densities of several deltas exceeded 1,000/km2 in 2000. The Pearl Delta recorded the highest population density, 1,694/km2, followed by the Nile, Yangtze, and Ganges which recorded 1,518/km2, 1,223/km2, and 1,220/km2, respectively (Table 2; Overeen & Syvitski, 2009).
• Many of the world’s largest cities are located in deltas. Some of the cities include: Shanghai (>23 million & density of >6,000/km2); Cairo (>22 million); Bangkok (>15 million); Dhaka (>7 million), and New Orleans (>1 million; Syvitski, 2016; http://worldpopulationreview.com).
Table 2. Population Growth and Densities of 31 Major Deltas of the World, 2000–2015
Population in 2000
Population in 2015
Population Growth or Decline (%)
Mean Population Density (pop/km2)
Average = 35
Average = 395
Source: Overeen and Syvitski (2009).
The beginning of the third millennium is characterized by widespread planetary-scale changes in the Earth’s system known as “global change.” The U.S. Global Change Research Act of 1990 defined global change as:
changes in the global environment—including alterations in climate, land productivity, oceans and other water resources, atmospheric chemistry, and ecological systems—that may alter the capacity of the Earth to sustain life. The main issues are climate change, desertification, deforestation, land use management, preservation of ecosystem and biodiversity, population and urban growth.
The world is currently experiencing the largest ever increase in population and urban growth (Table 3). Population, urban growth, and climate change are related, and most manifestations of climate change are attributed to human-induced impacts. Population density and growth are highest in coastal regions and deltas, which make these areas “frontlines” and “hot spots” of global change. The report of the Intergovernmental Panel on Climate Change (2007) indicated that climate-related changes in the 21st century will include an acceleration in sea-level rise, continuous increase in sea surface temperature, more extreme weather events, storm surges, altered precipitation, etc. According to the report, this could make 50% of the surface areas of deltas vulnerable to flooding and erosion. In summary, climate-related changes are expected to have a wide range of physical, economic, ecological, and social impacts, especially in coastal zones and deltas.
Table 3. Projected Population and Urbanization Growth
Africa & Asia
3.4 (50% of world)
6.7 (70% of world)
Source: Simonovic (2012).
Environmental Geologic Challenges in Deltas
Because deltas are important areas of high food productivity and exploitation of geologic resources, they pose great challenges to managers of water and land resources. Deltas are becoming increasingly vulnerable to flooding, climate change, environmental pollution, and environmental degradation because of the combined effects of the following factors: their low-lying coastal and riverside locations, continuous subsidence of most deltas, and rapidly increasing human populations, socioeconomic activities, and infrastructures. The trapping of sediments behind dams erected upstream poses one of the greatest threats to deltas worldwide. A global survey of the sediment loads of the world’s rivers revealed that the dominant global trend is decreasing sediment load (Walling, 2006, 2013; Walling & Fang, 2003).
The key environmental geologic challenges in delta areas (especially urban deltas) are: increasing exposure and vulnerability to geologic hazards (floods, cyclones, etc.), sea-level rise, sediment-load supply, contamination of soil and water resources, provision of adequate and safe drinking water, and safe waste disposal.
Vulnerability to Water-Related Hazards (Floods)
Flooding is a simple natural phenomenon that occurs when water overflows dry land that is not normally submerged (Ward, 1978). Floods are the most common and widespread of all geologic (natural) hazards and have resulted in more human deaths than all other hazards combined (including earthquakes). Floods are caused by a wide range of both geologic (precipitation is the major factor) and human-induced processes (Table 4). Flood magnitude and risk are largely determined by human activities both within and outside the delta area. Although the IPCC (2007) suggested that no catchment-data evidence had been found for a climate-related trend in the magnitude and frequency of floods in recent decades, it noted that flood damage was increasing.
Table 4. Factors Initiating and Modifying Floods
• Heavy rain
• Land drainage
• Rapid snow melt
• River regulation
• Channel straightening
• Rapid ice melt
• Interbasin transfer
• Flood protection works
• Glacial lake breaches
• Waste water release
• Ice breakup
• Water abstraction and irrigation
• Debris entrapment
Source: Simonovic (2012).
Water contributes to the prosperity of deltas, yet the same water poses several risks. Too much water causes floods, while lack of water causes drought, saltwater intrusion, and adverse impacts on the quality/quantity of freshwater resources, biodiversity, and the ecosystems. The global trend is a continuous rapid increase in water-related disasters (flood) and increasing exposure and vulnerability of deltas and low-lying coastal regions. Globally, water-related disasters already account for 90% of all natural disasters (Carien van Zwol et al., 2015). Table 5 presents recent major floods in some deltas and rivers.
Table 5. Recent Floods in Some Major Deltas and Coastal Cities
Mississippi (Hurricane Katrina)
Mississippi River Flood
Yangtze River Flood, China
• About 85% of the world’s major deltas experienced severe floods in the past decade.
• Coastal erosion, accelerated rates of sea-level rise, subsidence, and land loss resulting mainly from decreased sediment supply are responsible for the high flood risk confronting human populations in most deltas.
• A significant number of deltas are sinking because of the effects of flood-control structures and other human-induced changes to the river systems.
• Flooding will affect more than one million people directly by 2050 in three megadeltas (Ganges-Brahmaputra, Mekong, and Nile); more than 50,000 people are likely to be directly impacted in each of nine additional deltas, and more than 5,000 in each of an additional twelve deltas.
• About 75% of the population affected live on Asian megadeltas and deltas, and a large proportion of the remainder are on deltas in Africa.
• A combination of sinking deltas and rising seas will continue to increase the damages caused by hurricanes and other flooding events in the future.
The Mississippi Delta is a typical example of a sinking delta: the sinking is attributable to the effects of the extensive artificial levee system built along the river and the removal of the delta’s oil and gas reserves over a very long period.
Managing Flood Hazards
There is increasing emphasis on an integrated approach in modern flood management (World Meteorological Organization, 2009) and on maintaining a rational balance between structural and nonstructural infrastructures. Reducing the risk of natural flood disasters should focus not only on reducing the likelihood of flooding, but also on increasing the resilience in coping with them when they occur. This implies preventing large number of casualties and major economic damage. Integrated flood management shifts focus from flood control to flood management and integrates land use, water resources, and risk management in river basins under the framework of integrated water resources management (IWRM).
Proactive flood risk management generally involves closely interconnected components, namely: prevention, protection, preparedness, mitigation, response, and recovery. Prevention is the cornerstone of disaster risk management. Effective implementation of this approach requires a paradigm shift from the traditional focus on mitigating the (direct) impacts of disasters using stand-alone and ad hoc interventions to an integrated approach with emphasis on prevention, mitigation, preparedness, and vulnerability reduction.
Declining Fluvial Sediment Load and Increasing Subsidence
There is a strong relationship between sediment load/deposition and delta subsidence. The elevation of deltas above sea level is controlled by four interrelated factors: the ocean’s global volume, sediment deposition, sediment compaction, and vertical movements related to plate tectonics. Fluvial sediment load is a critical factor controlling the evolution and stability of deltas. Generally, a decline in the sediment load reaching the delta impacts negatively on the delta-building process. Studies have shown that declining sediment load accelerates delta subsidence (Syvitski et al., 2009; Walling, 2011, 2012, 2013).
The change in the sediment load of rivers associated with deltas has been studied by several researchers (Gupta et al., 2012; Milliman & Famsworth, 2011; Milliman et al., 1989; Vorosmarty et al., 2003, 2009, 2010; Walling, 2006, 2013; Walling & Fang, 2003). Table 6 summarizes the results of their studies. The results suggest that decreasing sediment load is the dominant trend. Trapping of sediment by dams constructed upstream of the delta is the primary factor responsible for the decrease in the sediment load of most rivers and deltas. Other secondary factors include soil conservation, sand mining, and sediment control. Since dam construction and soil conservation works started in the second half of the 20th century, declining sediment load is essentially a post 1960s problem. In isolated cases, an increasing sediment load may be caused by land clearance, catchment disturbance, poor management of agricultural land, deforestation, and other activities.
Table 6. Changes in Sediment Load of Some Major Rivers and Effects on Delta Areas
Sediment load (Mt/year)
% Size Reduction
% Size Increase
Subsidence (cm/ year)
Ten rivers in China emptying into Pacific Ocean
From 2987 to 575
All Rivers in East, Southern, & SE Asia
Past 50 years
From 4435 to 2240
Past 50 years
Past 50 years
Past 50 years
Past 50 years
Past 50 years
1964, after closure of Aswan Dam
From 120 to 0.1
Past 50 years
Past 50 years
Past 50 years
Kolyma (Eastern Siberia)
Source: Walling (2013).
Environmental Degradation and Pollution
Deltas are highly susceptible to environmental degradation and pollution because of:
• Their position at the lowest point of the downstream section of rivers
• Their extremely dense human population, urbanization (megacities), and high agricultural, maritime, and industrial activities
• Exploitation of fossil fuels (oil, gas), and other natural resources.
Under natural conditions and favorable climatic setting, the self-maintaining nature of the delta system ensures continuity of its resources and structure. However, direct and indirect impacts of human activities tend to alter the natural geodynamic equilibrium, resulting in deterioration of the environment. The major environmental degradation and pollution issues in deltas are: pollution of water and land resources, mangrove and forest degradation, loss of fisheries, loss of biodiversity, and saltwater intrusion. The differences in the extents of environmental degradation and pollution in deltas across the world can be attributed to the intensities of the various human activities both in the delta area itself and in the upstream section of the river catchment. Well-documented examples of severe environmental degradation and pollution in deltas include those of the Niger, Pearl, Mississippi, and others. The primary causes of environmental degradation and pollution in some selected deltas are summarized in Table 7.
Table 7. Primary Causes of Environmental Degradation and Pollution in Some Deltas
Key Environmental Issues
Niger Delta (Nigeria)
Pearl Delta (China)
Mississippi Delta (USA)
Irrawady Delta (Myanmar)
Rhine-Meuse Delta (German—Netherlands)
Groundwater Resources and Contamination
Although abundant freshwater resources (surface and groundwater) occur in deltas, their quality and quantity are greatly affected by human activities and global change. High water demand is associated with deltas that are characterized by high population density and intensive agricultural and industrial activities. Attempts to meet high water demands in deltas can easily lead to over abstraction of groundwater resources, which can, in turn, lead to saltwater intrusion and contamination. The severity of water resource development and management problems in any delta depends on the population, levels of urbanization and economic development, size, height above sea level, and agricultural and industrial activities. As would be expected, the problems of water resource development and management are most severe in deltas in developing countries that are characterized by high population density and intensive agriculture.
Groundwater resources in deltas are prone to contamination because of the generally shallow groundwater level, which may be less than a meter below ground in some areas. Groundwater is the main source of the domestic and municipal water supply in deltas in developing nations and its abstraction is uncoordinated and unregulated. There is urgent need for proactive legislation and enforcement to prevent contamination and saltwater intrusion in developing countries. Surface water in deltas is also prone to contamination from maritime activities and spill from oil and gas exploration/production wells (both onshore and offshore) in petroleum-rich deltas like the Mississippi and the Niger.
Although the provision of water for socioeconomic development is beneficial, it is often accompanied by a significant adverse impact on the ecosystem and biodiversity (Vorosmarty et al., 2010). Currently, 1.6 billion people live in river basins with severe water stress. With a business-as-usual scenario, this number will increase to 3.9 billion by 2050 (OECD, 2012). At the current population and economic growth rates, global water demand will exceed available water supply by 40% by the year 2030 (The 2030 Water Resources Group, 2009). Global climate change will exacerbate these challenges; therefore, water resources must be protected from the variabilities of the changing Earth. Sustainable water management at the local, river basin, delta, city, and regional levels depends on safeguarding water resilience at the Earth-system scale (i.e., ensuring that human development takes place within the ecosystem’s carrying capacity of the Earth system). Therefore, sustainable water management in deltas must not only consider all natural processes and human activities in the entire river catchment, but also global climate change and the Earth system’s water resilience.
The problems of waste management, especially in urban centers, including those in deltas, are well known. A unique problem in deltas is that of finding suitable sites for modern landfills for waste disposal. One of the key geological requirements is adequate depth to the groundwater level (>20 m) to prevent contamination by leachate from the waste. Unfortunately, the depth to the groundwater level in most deltas is quite small (less than a meter), so other waste-disposal options should be explored. Options include “raised sanitary landfill” and incineration. In the raised sanitary landfill technique, the proposed landfill site is raised by about 3 to 6 m before construction in order to prevent easy contamination of the groundwater. In addition, artificial lining with synthetic impermeable membranes, combined with cementation with bentonite or other related materials, is required to eliminate percolation of leachate into the groundwater aquifer. Furthermore, peripheral trenches must be provided around the landfill to drain and collect the leachate, which is thereafter disposed of in an environmentally acceptable manner to prevent risk of groundwater and surface water contamination. Different types of incineration systems are available and the type preferred will depend on local socioeconomic conditions, expected volume of waste, and the level of technological advancement.
Challenges Facing Deltas in Developing Nations: The Case of the Niger Delta in Nigeria
The Niger Delta (Figure 2) covers an area of approximately 70,000 km2. It is the largest delta in Africa and the third largest in the world. In political context, the Niger Delta consists of nine of the 36 states of the Federal Republic of Nigeria. The current population of the Niger Delta is about 40 million (24% of Nigeria’s total population) and is projected to reach about 45 million by 2020 (Table 8; NDDC, 2006). The ecology of the region is very sensitive and complex, consisting of saltwater mangrove, freshwater swamps, freshwater meander belts and flood plains, coastal/barrier islands, and tropical rainforests.
Table 8. Population Projections for the Niger Delta States
Source: Population.gov.ng (2006).GTZ projections (2004). Based on National Population Commission.
Subsistence agriculture and fishing are the major livelihood activities of the local residents. It is estimated that a sea-level rise of one meter would lead to submergence of up to 20% of the Niger Delta (Awosika & Folorunsho, 2006).
The Niger Delta is rich in oil and gas reserves, which account for over 85% of the country’s foreign exchange earnings. Adverse environmental impacts and social conflicts related to oil and gas exploitation in the Niger Delta have been widely reported. (After a lull of over 6 years, in the beginning of 2016, vandalization of petroleum industry facilities was renewed.) Despite the economic importance of the Niger Delta, the region is generally underdeveloped, with poor socioeconomic infrastructures and high levels of poverty and youth unemployment. According to the World Bank Report (2008):
The Niger Delta’s abundant natural resources, especially its oil, might have been expected to constitute a foundation for the region’s development and prosperity. However, the reverse is the case: perhaps more than anywhere in the world, the Niger Delta exemplifies the paradox of low development in an environment of rich resources.
Several successive intervention bodies were set up at various times by the Federal Government of Nigeria to focus special attention on the development of the difficult terrain of the region and its people. Table 9 presents the key intervention bodies and their major achievements.
Table 9. Major Intervention Bodies in the Niger Delta and Their Achievements
Sir Henry Willink’s Commission
Niger Delta Development Board
Niger Delta Basin Development Authority (NDBDA)
Presidential Task Force Account for Niger Delta Development
Oil Mineral Area Development Commission (OMPADEC)
Niger Delta Development Commission (NDDC)
Ministry of Niger Delta Affairs (MNDA)
The intervention bodies that are currently involved in the development of the Niger Delta include the Niger Delta Basin Development Authority (NDBDA), Niger Delta Development Commission (NDDC), the Ministry of Niger Delta Affairs (MNDA), other relevant federal government ministries/agencies, state and local governments, community groups/civil society organizations, oil and gas companies, and other private-sector groups. From the communities’ perspectives, the various interventionist bodies have failed to meet the people’s expectations of rapid and sustainable socioeconomic development. The unsatisfactory performance may be attributed to several factors, key among them being inadequate planning, absence of an integrated strategic plan developed through a bottom-up approach, poor funding, and lack of prudent management of funds. The various development activities executed by the intervention bodies do not appear to follow any specific holistic development vision, strategy, or implementation plan formulated for the Niger Delta with active participation of all stakeholders. The majority of the ad-hoc development projects of the NDDC do not follow the well-articulated implementation plan specified in the NDDC Strategic Master Plan.
Petroleum Industry, Environmental Degradation, and Pollution
Oil and gas exploration started in the Niger Delta in 1937, and the first oil well was struck in 1956. The first shipment of oil exports was in 1958, and daily production rose rapidly to a peak of over 2.4 million barrels by the 1980s. Numerous oil spills (onshore and offshore) have occurred during the over 55 years of oil and gas industry activities in the Niger Delta, resulting in severe hydrocarbon contamination of soil and water resources (Figure 3).
The 2011 report of the UNEP Environmental Assessment of Ogoniland (Eastern Niger Delta) documented extensive environmental pollution in the area. The report estimated that the environmental remediation of Ogoniland will take between 25 and 30 years. It would take a much longer period to clean up the entire Niger Delta region. Contamination of the rivers, creeks, groundwater, and soils of the region has destroyed the traditional livelihood activities (fishing, farming, etc.) of the communities, thereby exacerbating poverty and unemployment. In 2016, five years after the release of the UNEP study report, the federal government officially inaugurated the commencement of the Ogoniland clean-up/restoration exercise. It should be emphasized that, even if adequate planning and funding are provided, two community-related key issues have to be addressed in order to achieve a sustainable effective clean-up/restoration of Ogoniland and the Niger Delta. These issues are:
1. The prevalence of poverty in the affected communities, whose members currently prefer payment of cash compensation rather than engaging in actual environmental clean-up/restoration
2. The affected communities’ lack of adequate understanding of the importance of healthy ecological systems to socioeconomic development and human health.
These factors are partly responsible for lack of community buy-in or ownership of the clean-up programs. In other words, focusing on the clean up of hydrocarbon-contaminated sites in Ogoniland or the Niger Delta without addressing related societal issues (especially poverty, youth unemployment, insecurity, artisanal refining, lack of infrastructure, and others) is only addressing part of the larger problem—the lack of sustainable development and management of the Niger Delta. The Ogoniland clean-up should therefore be undertaken within the context of an integrated, multisectoral, and holistic strategic plan comprising a long-term vision and several short-term sectoral objectives.
The 2012 flood in Nigeria (Figure 4) has been described as the most severe and devastating in the nation’s modern history. It displaced 2.3 million people and killed over 363 people, and the combined economic losses (infrastructure, physical/durable assets, and economic activities across all sectors) were estimated to be approximately $16.9 billion.
The Niger Delta region suffered the most extensive devastation because of its location in the lowest part of Nigeria, where the Niger and Benue rivers empty their waters into the Atlantic Ocean (Figure 5). Flood heights in the Niger Delta reached 8 m above the normal seasonal water levels. The floodwaters inundated most parts of the central Niger Delta for 6 to 8, weeks causing severe negative impact on flora and fauna. The primary causes of the flood were:
• Heavy rainfall between July and September 2012, resulting in accumulation of enormous volumes of water in the Niger and Benue rivers.
• Release of excess water from the Lagdo Dam on the River Benue, located in Cameroon, about 100 km upstream from the Nigeria–Cameroon border. The excess water was released between August 24 and September 26, 2012, and this caused the water level at the confluence of the Niger and Benue rivers at Lokoja to rise to an unprecedented height of 12.84 m, with a discharge of 31,692 m3/s, compared to the normal values of about 5.59 m and 15,000 to 20,000 m3/s, respectively.
Nigeria is the southernmost country in the Niger and Benue drainage system. The rivers flow through several countries in West Africa (Guinea, Mali, Niger, and Cameroon); therefore, the flooding and water-supply issues of the drainage basin system require international cooperation and collaboration among all the countries within the basin. Although some preliminary discussions have taken place, the required regional cooperation is weak (Bamigboye, 1990; Pare & Bonzi-Coulibaly, 2013). For example, there is no memorandum of understanding (MOU) or joint consultative mechanism among the various countries regarding the management of transboundary waters of the drainage basin. This is in contrast to the high levels of cooperation and partnership that exist in the Nile Delta Initiative, which was formally signed in 1999 by Egypt, Sudan, Ethiopia, Uganda, Kenya, Tanzania, Burundi, Rwanda, the Democratic Republic of Congo (DRC), and Eritrea (as an observer).
The devastating impact of the 2012 floods in Nigeria was exacerbated by poor land-use planning, nonadherence to building codes, and erection of houses on flood plains. The floods revealed the serious problems/deficiencies in Nigeria’s flood disaster management strategies, especially prevention and response mechanisms. For example, the devastating impacts of the flood would have been greatly reduced in down-stream areas and in the Niger Delta if there had been accurate predictions of the dates the floodwater would reach and attain peak heights at various locations and vulnerable populations and property had been evacuated. The floods started peaking in late August in northeastern Nigeria and took about two months before peaking in the Niger Delta in October. At the time the floods occurred in 2012, there were no Hydrological/Flood Modeling/Forecasting Centre and Flood Early Warning Systems in the country. There were also no river gauging stations or strong hydrological data gathering/monitoring processes in the Niger Delta at that time. The same situation still exists in 2017. No doubt, this is a reflection of the weak institutional capacities of the relevant agencies, such as the federal and state Ministries of Water Resources, Niger Delta Basin Development Authority, the Niger Delta Development Commission.
A total of four dams have been built in the upstream sections of the Niger and Benue rivers. Over time, these dams have resulted in a reduced sediment supply to the delta (Abam, 2001) and in the deposition of sediments in the river channels. This decreases the channel’s depth (channel siltation) and the volume of water it can accommodate, which increases flood risk in the adjoining deltaic plains.
Provision of Water Supply
The Niger Delta region is endowed with abundant groundwater resources, which occur in the Benin Formation and Coastal Plain Sands that form the major regional high-quality aquifers. Although the regional aquifers extend beyond 1,000 m in depth in several locations, most groundwater abstraction in the region is currently concentrated in the top 300 m. Groundwater occurrence in the freshwater and saltwater mangrove swamps is characterized by localized, shallow, unconfined aquifers and deeper, laterally more extensive aquifers that are generally subdivided into a series of aquifers/subaquifers by clay units (Akpoborie, 2011; Akpoborie & Aweto, 2012; Akpoborie et al., 2011; Akpokodje, 1987; Akpokodje et al., 1996, 1998; Amadi, 2004; Amajor & Ofoegbu, 1989; Etu-Efeotor & Akpokodje,1990; Etu-Efeotor & Odigi, 1983). Between three and five aquifer horizons have been identified (Table 10) and the majority of the existing water boreholes utilize the top four aquifer layers.
The problem of saline water intrusion arising from mismanagement is common in coastline towns (e.g., Bonny, Brass, and Escravos) and some towns further inland that are close to the boundary between the freshwater and saltwater mangrove swamps (e.g., Port Harcourt). Another major groundwater quality problem is the widespread occurrence of high-iron-content groundwater. The factors controlling the lateral and vertical distribution of high iron concentration in groundwater in the Niger Delta are not clearly understood.
Currently, about 60% of the Nigerian population has access to a potable water supply, but the figure is only about 30% in the Niger Delta (Federal Ministry of Water Resources, 2011). The inadequate supply of safe drinking water in the Niger Delta region is principally due to underdevelopment of the groundwater resources. Other important contributing factors include weak institutions, inadequate policies, poor implementation of existing policies, and generally poor water-resource management practices. In addition, little attention has been paid to climate change and adaptation to it.
Table 10. Typical Utilization of the Various Aquifer Horizons in the Niger Delta
Depth range (m)
Groundwater abstraction and degree of saltwater intrusion
All small private boreholes, most extensively exploited, causing water table decline and saltwater intrusion along the coast.
Medium-size boreholes, community/municipal/industrial boreholes. Moderate exploitation & moderate saltwater intrusion
Some community/municipal/industrial boreholes. Limited exploitation & limited saltwater intrusion.
Few large-scale deep boreholes for municipal & industrial water schemes, no saltwater intrusion.
Few large-scale deep boreholes for municipal & industrial water schemes, no saltwater intrusion.
Source: Etu-Efeotor and Akpokodje (1990).
Municipal waste collection and disposal in all state capitals and some other major urban centers in the Niger Delta are poorly organized. Generally, in the absence of properly engineered and operated landfills, wastes are dumped on open dry land and roadsides, into swamps and waterfronts, or into drainage channels. There are no public-agency-owned sewage treatment plants in the Niger Delta region.
Research and Data Acquisition Systems
In most developed countries of the world, emphasis is given to acquisition of relevant data through research and continuous monitoring/field observations in the sustainable management of floods and other natural disasters. Several research activities are always initiated after major flood disasters to, among other things, investigate the lessons learned and to improve the management of future disasters. For example, the Research Programme Framework of the European Union funded a total of 30 research projects after the European floods of 2000–2002 (Plate, 2011).
The response to Nigeria’s flood of 2012 was different. Although the federal and state governments and private organizations spent billions of naira on the emergency response, rescue/recovery, and resettlement activities, and also organized several conferences, seminars, symposia, and workshops, the amount of funds spent on major research projects to acquire relevant data was grossly inadequate. This reflected lack of mainstreaming of research and data acquisition in the country’s disaster management strategy and activities of the intervention bodies. No major study or systematic field monitoring regarding the management of natural disasters has been undertaken in the Niger Delta apart from the 1957 NEDECO study report “Waters of the Lower Niger River Basin” and the 1980 Korean DPR Report “Investigation of Possible Flood Protection Measures in the Nun and Forcados River Area.”
As noted in the Background section, modern flood mitigation calls for a paradigm shift from a reactive approach to an anticipatory response approach that includes adequate flood preparedness (i.e., all activities taken in preparation for the flood, including identification and mapping of flood-prone and vulnerable areas and other relevant information). In a watershed, this requires detailed knowledge and accurate data on the flood risk in different locations. Flood risk and vulnerability maps show the locations where people, the natural environment, and property are at risk during flood hazards. Once the flood-vulnerable areas have been demarcated, proper precautionary measures can then be taken to ensure adequate preparedness, effective response, quick recovery, and effective prevention. There are no standard published flood risk/hazard/vulnerability maps (regional or local) of the Niger Delta Basin.
Unlike typical deltas, where a river divides into multiple tributaries that flow directly into open-water systems (such as lakes, seas, or oceans), in inland deltas, the rivers form multiples tributaries that flow directly into inland lowlands, valleys, depressions, or floodplains. In some inland deltas, the multiple tributaries may rejoin and continue into the sea. Typical examples of inland deltas include the River Niger Inner Delta (or Inner Niger Delta) in Mali, the Okavango Delta in Botswana, the Peace-Athabasca Delta in Alberta, Canada, and the Saskatchewan River Delta (SRD), which straddles the border between the provinces of Saskatchewan and Manitoba in Canada. Some inland deltas are endowed with high-quality tourism attractions, unique biodiversity (Okavango Delta is a UNESCO World Heritage Site), and fertile agricultural lands. The majority of inland deltas do not have large urbanized cities and the traditional livelihood activities consist of rural small-scale farming, animal rearing, forestry, and micro-scale mining. Some publications on inland deltas include Mahe et al. (2009, 2013), Mbaiwa (2005), Sagin et al. (2015), and Wheater and Gober (2015), just to mention a few.
Although the environmental geologic and sustainability challenges in inland deltas may vary locally, the major challenges common to most of them are:
• Large variations in water resource availability and in hydrological systems, caused by the combined impacts of climate change/variability and upstream use of water
• Annual flooding and drought, with devastating effects on the livelihood activities of the rural inhabitants
• Degradation of land resources (deforestation) and loss of fisheries, wildlife, and biodiversity mainly caused by unsustainable use
• Environmental pollution.
The majority of intervention programs initiated in inland deltas are designed to:
• Enhance the resilience of the rural population by raising awareness of integrated natural resource management and of the underlying causes of climate change, its implications, and adaptation measures
• Improve the socioeconomic conditions, in terms of food and livelihood security, for rural small-scale farmers
• Encourage well-designed agricultural landscape schemes (watershed management) to maintain forest ecosystems and to enhance water storage, erosion control, biodiversity conservation, and soil rehabilitation
• Enhance well-managed and sustainable tourism activities with minimal environmental impact.
Sustainable Management of Deltas: The Relevance of Environmental Geology
The formation of river deltas involves two major interconnected geologic processes: transportation and deposition of sediments. The two processes are affected by changes in climatic, hydrological, and human-induced conditions. Natural flooding is an integral part of the delta-building process because during flooding, rivers overflow their banks and deposit sediments over the delta plains and abandoned river channels. This results in the formation of multiple layers of fine-grained older and younger alluvial sediments. A delta will continue to enlarge if sedimentation dominates over processes that degrade deltas (such as sea-level rise, subsidence, and coastal erosion).
In the past 60 years, there has been significant reduction in the size of several deltas because of human activities (Table 11) that have resulted in decreased sedimentation as well as increased subsidence and coastal erosion, which are further exacerbated by climate change. Since deltas are formed by geologic processes, the application of geologic knowledge is imperative, not only for understanding how and why deltas respond to emerging global pressures, but also for formulating effective protective/restoration measures in a rapidly changing global environment. The problem-solving interdisciplinary nature of environmental geology (“application of geologic principles and knowledge to problems caused by man’s occupancy and exploitation of the physical environment”) and its focus on integrated earth-science knowledge give the discipline an advantage in applying geologic knowledge to provide solutions to the challenges facing deltas (Figure 6). The upper section of Figure 6 shows that emphasis on interdisciplinary and integrated Earth-science knowledge is more relevant in the description of the components of the Earth’s environment and associated issues. The lower section of the figure shows the critical geologic controls/factors that must be known and integrated in the formulation of sustainable solutions to the problems facing deltas and to achieve a sustainable global environment.
Table 11. Human-Induced Delta-Degrading Factors and Activities
Human Activities Causing Delta Degradation
Increased coastal erosion
Day et al. (1997) defined the sustainability of deltas from three perspectives: geomorphology, ecosystem, and economics (Table 12). It is therefore logical that the sustainable management of deltas should incorporate these three perspectives in an equitable manner. This is in contrast to traditional approaches, which tend to focus on harnessing the economic potential of deltas almost to the exclusion of the other perspectives.
Table 12. Sustainability of Deltas
No change in vertical and horizontal dimension. No change in total surface area of delta, and wetland surface elevation balances sea-level change.
No change in total net primary productivity (NPP) of ecosystems over the decadal time scale. Conversion of deltaic wetlands to open water or uplands lowers NPP.
Output of goods and services is greater than the economic inputs or subsidies required for production. Analysis of economic sustainability of deltas is complicated.
Source: Day et al. (1997).
The earlier traditional approach of engineers and scientists to the water-related problems of deltas was to create a network of canals to improve access and water circulation by the construction of levees, dikes, closure dams, and storm-surge barriers. These structures significantly altered the natural sedimentation processes and resulted in trapping of sediments and progressive loss of wetland, total aquatic biota, biodiversity, and ecological value of the delta system. However, recent events and experiences in delta management have led to a paradigm shift from the traditional approach of containing water by building higher dikes and walls to a more integrated, holistic, adaptive, and ecologically based philosophy of building with nature, instead of fighting it. Some examples of publications in support of this paradigm shift include:
• Declaration of the 30th Annual Meeting of the International Council of the Academies of Engineering and Technological Sciences (CAETS), Delft, The Netherlands, June 27, 2008:
Living in deltas has always required human intervention. Often, this intervention conflicts with the natural environment, requiring constant maintenance and further intervention, which in turn leads to degradation of the overall conditions in these areas. The aim of “Building with Nature” is integrated delta development making use of the forces, interactions and materials present in nature. New design methods are elaborated to optimize the opportunities offered by natural ecosystems. Sustainable development of flood-prone regions can be achieved only when flood protection itself is sustainable. This calls for a flexible, adaptive approach and strategy of building with rather than against natural processes.
• Molennaar et al. (2013, p. 93):
The use of engineered solutions for narrowly defined problems has in recent times proven insufficient to combat the complex, intertwined challenges confronting modern delta living. Considering the fact that climate change and continued subsidence will increase challenges further, New Orleans may need to embrace a more holistic, ecologically based thinking with the cultivation of nature’s own line of defense.
• The Delta Approach (2013, p. 15):
The Room for the River Program uses a globally innovative approach to protect areas against river flooding. Giving the river more room (e.g., by moving dikes, digging secondary channels and deepening flood plains), not only protects the delta regions from floods, but also improves the overall quality of the area with new nature and recreational areas as an added bonus.
From the geological perspective, the Earth and its environment (including deltas) were formed by geological processes that acted in the past and are still active today according to established geologic knowledge and principles. These are the critical geological controls of the natural environmental that are susceptible to alteration either directly or indirectly by human activities. The critical geologic controls include: the geological/depositional history, stratigraphy, depositional environment, and the properties of the alluvial sediments. If these geologic controls are not known, it is impossible to formulate appropriate measures that can effectively address the problems threatening the sustainability and stability of deltas.
To apply geologic knowledge and principles to providing sustainable solutions to challenges facing deltas worldwide, there must be close and functional communication between environmental geologists and all other stakeholders involved in delta management. In Figure 6, this is represented by the two lower arrows pointing to the left. Traditional management approaches have significant adverse impact on the sustainability and stability of deltas, partly because there has been either no or insufficient application/integration of geologic knowledge and principles. The recent paradigm shift in favor of a more integrated, holistic, adaptive, and ecologically based philosophy of building with nature emphasizes the physical components of the Earth system (especially, geology, hydrology, and geomorphology), which have hitherto received little attention.
In addition to the integrated approach, there is the growing global consensus that international cooperation that cuts across disciplines, sectors, and regions and that also incorporates good policy and governance is required to effectively address the challenges facing deltas and to achieve their sustainable management. Some of the major international initiatives include:
Formation of Connecting Delta Cities (CDC) networks
World Estuary Alliance (WEA), launched at the WEA Conference (June 6–8) in Shanghai
First international conference “Deltas in Times of Change”
Establishment of Delta Alliance International as a foundation under Dutch law with offices in several regions of the world
World Delta Summit (November 21–24, 2011) in Jakarta, Indonesia
Ten-year “Global Delta Sustainability” initiative launched by the International Association of Hydrological Sciences (IAHS)
International conference “Deltas in Times of Change II” in Rotterdam
Delta Coalition launched in Sendai, Japan, by group of national governments to promote “global discussions on deltas in sustainable development”
First International Conference on Deltas and Rivers in Africa (October 16–18), University of Port Harcourt, Nigeria. A new network, named “Africa’s Rivers and Deltas Network” (ARDNet), and Initiative for Sustainability of Africa’s Rivers and Deltas (ISARD) were formed at the conference.
A literature search revealed a large number of publications on each of the three subthemes of this discussion—river deltas, environmental geology, and sustainability—which is a reflection of their importance to human society and the continuously evolving nature of our understanding of the issues involved. Concern about adverse environmental impacts of human activities cuts across the three subthemes. One of the greatest challenges of the 21st century is the increasing negative impact of human activities on the Earth’s environment, which is the central issue in the concept of sustainable development.
The concepts of sustainable development and sustainability science stipulate that human economic and social development should take place without irreversible damage to the carrying capacity of the Earth’s natural environment and without significant depletion of nonrenewable resources (WCED, 1987). The sustainable management of the Earth’s finite natural resources in the face of unprecedented global population growth and climate change is a major challenge currently facing human society. Geologic resources, as traditionally defined, mainly consist of energy and mineral resources, which are generally nonrenewable. Currently, the overexploitation of virtually all geologic resources is in conflict with the goals of sustainable development and sustainability. Sustainable development is the process of development from the present unsatisfactory state of resource and environmental management to the ideal state of sustainable global human society. At the global level, the concept of sustainable development has become an integral part of both public and private activities and a key mission of research institutions and universities. Despite this, the problem of translating the concept of sustainable development into operational/practical criteria still exists, because of the several variables (social, economic, environmental, cultural, and technical) that must be considered simultaneously.
A recent global survey of publications on the theme of sustainable development and sustainability (Battencourt & Kaur, 2011) revealed that only about 5% of publications on the subject came from the geology discipline, compared to 34%, 23%, and 21% from the social sciences, biological sciences, and engineering disciplines, respectively. Considering the fact that geology is the study of the Earth, the 5% contribution by geologists to sustainable development and sustainability publications is grossly inadequate. In order to enable geology to play a more active role in sustainable development and sustainability issues, there should be a paradigm shift from the traditional study of planet Earth as isolated discrete components, to the concept of an integrated whole Earth system (Earth system science). This involves knowledge of all the components of the Earth system (atmosphere, hydrosphere, biosphere, cryosphere, and geosphere) and the interactions among them. The paradigm shift should also embrace a systems thinking approach. In the most general sense, a system is a collection of elements linked by strong interactions that are more important and greater than the sum of the parts. A system approach allows a wider variety of factors and interactions to be taken into account.
Several approaches have been advanced to address the complex issues of sustainable management of resources and environment. Environmental geology, environmental science, and sustainability science are among the applied science disciplines with focus on the protection of the quality of the environment. Applied science disciplines use different disciplinary knowledge and expertise to provide solutions to environmental issues through multidisciplinary, interdisciplinary, or transdisciplinary approaches. Both environmental geology and environmental science use an interdisciplinary research approach, while sustainability science uses a transdisciplinary approach. Interdisciplinary research can be defined as the use of a wide spectrum of scientific disciplines brought together to solve complex problems, while transdisciplinary research integrates different scientific disciplines and nonacademic participants, interested stakeholders, and community groups. Unlike interdisciplinary and transdisciplinary research, which are able to resolve discrepancies between participants and explore synergies through an iterative research process, multidisciplinary research simply ensures that the required expert opinion on the issue is provided.
The concept of integrated management of resources evolved to ensure better management of resources through the involvement of different stakeholders and policymakers. Two good examples of this concept are integrated water resources management (IWRM) and integrated natural resources management (INRM). The major shortcoming of the integrated management concept is its focus on a single resource without giving consideration to the interdependence of resources. One approach that integrates management and governance across sectors and scales, and also considers the interdependence of resources, is the nexus approach, which emerged in the early 1980s (Hoff, 2011). The nexus approach is based on the understanding that vital environmental resources are strongly interconnected and require an integrated perspective to manage them sustainably (Schwarzel et al., 2015). Such a nexus approach must take into account different sectors and disciplines in both research and capacity development and strive for a holistic management strategy. Typical examples of well-developed nexus approaches include those for water–soil–waste, energy–water, poverty–environment, soil–climate, food security–natural resources, and others. Although an integrated and holistic resource management approach encompassing all disciplines and sectors has been recognized and recommended, sectoral and disciplinary approaches are still prevalent in practice. This situation appears to be even more prevalent in developing countries.
Geological processes responsible for the formation of river deltas are increasingly being altered by human activities and this threatens the survival of the river deltas and the millions of human inhabitants of deltas. The major consequences of intense human activities on river deltas are submergence, flooding, and environmental degradation. The key environmental geologic challenges in delta areas (especially urban deltas) are: increasing exposure and vulnerability to geologic hazards (flooding, cyclones, etc.), sea-level rise, sediment-load supply, contamination of soil and water resources, provision of adequate quantity and quality of drinking water, and safe waste disposal. The severity of these problems is higher in deltas located in developing countries due to the paucity of the required funds and expertise as well as very high human populations. To provide sustainable solutions to the changing geologic processes in river deltas and to ensure their future sustainability, there must be thorough understanding of the known and unknown driving processes of change in river deltas, prediction of their impacts, and utilization of the knowledge to develop and optimize management solutions.
The increase in infrastructure and environmental and agricultural projects in delta areas provides a unique opportunity to expand the role and scope of environmental geology in the context of sustainable development and sustainability. The question to be asked is, how much emphasis is placed on engineering/environmental geological knowledge and experience in the selection of consultants and contractors for major projects? Unfortunately, despite the generally accepted importance of environmental geology input in these projects, the engineering/environmental geology profession is still perceived as a “service agent” to be used on an ad-hoc basis rather than a fundamental component of major engineering/environment-related projects. To reverse this attitude, there must be deliberate efforts to ensure close and functional communication between engineering/environmental geologists and all other professionals and stakeholders involved in working toward the achievement of sustainable development and sustainability.
Human society is currently facing several unprecedented global challenges (exponential population growth and urbanization, resource depletion, and food, water, and energy security, environmental sustainability, climate change, natural hazards, poverty, etc.) that threaten the future of humanity and the integrity of the carrying capacity of the earth’s ecosystems (World Economic Forum, 2013). Traditional discipline-based knowledge, methodologies, and approaches are no longer sufficiently effective in addressing these complex and interconnected global problems, which cut across disciplines, sectors, and regions. An inclusive, holistic, and interdisciplinary (or multidisciplinary) approach is required.
Deltas are known globally for their great economic and environmental importance. However, their sustainability and stability are under increasing and profound threat from rise in sea level, climate variability, growth in human population, and urbanization, as well as the disproportionate impacts of human activities. The emergence of environmental science, environmental geology, and sustainability science is spurred by the concept of sustainable development, which has now attained global dimensions and constitutes the central goal of governments and human societies. Environmental science emphasizes the need for integration of all disciplines in addressing global environmental issues, while environmental geology primarily focuses on the application of geologic knowledge and principles. Sustainability science aims at the ambitious goal of achieving a truly sustainable global society by integration of knowledge from all disciplines and also bridging the gap between theory, practice, policy, and governance.
Until recently, most of the traditional engineered solutions to enhance the sustainability and stability of deltas were designed to keep out water. However, they tend to reduce the natural delta-building processes, rather than building with nature. The natural delta-building processes are mainly geological; therefore, a thorough knowledge of the causative geological controls of the problems confronting deltas is critical. The recent paradigm shift to a more integrated, holistic, and ecologically based solutions incorporates some critical aspects of the geological and hydrological perspectives. A key challenge, however, is the establishment of a close and functional communication between environmental geologists and all other professionals and stakeholders involved in delta management.
As shown by the Niger Delta example, the major unique challenges to sustainable management of deltas in developing countries include:
• Low levels of technical expertise, experience, and collaboration across sectors and disciplines
• Weak institutions, research, data acquisition, and field monitoring systems
• Poor funding and policy/governance
• High population growth and density
• Widespread poverty
• Low level of environmental awareness.
The following colleagues read the draft of this article at various stages: Prof. N. P. Okoh, Dr. C. A. Tse, Dr. F. D. Giadom, and Prof. Macaulay Mowarin.
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