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date: 17 August 2017

Environmental Geology of Deltas

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Environmental Science. Please check back later for the full article.

Deltas have played a significant role in the growth of human civilization because of their economic and ecological importance, and their recurring water related hazards. They are endowed with abundant natural resources (oil, gas, water, etc.), highly productive agricultural land, rich biodiversity, extensive wetland ecosystems, and waterways. Deltas cover about 1% of the earth’s surface, with an estimated total human population of over 500 million and an average density of about 500/km2. The combined population of the Ganges-Brahmaputra, Yangtze, and Nile deltas in 2000 was 230 million, which was expected to increase by 35% in 2015. Some of the world’s large urban cities (Shanghai, Bangkok, Dhaka, Cairo, New Orleans, etc.) are located in deltas.

Globally, urban deltas and associated coastal regions are becoming increasingly vulnerable because of the impact of intensive human development, high population growth, climate change, and sea level rise. In addition, a significant number of the world's major deltas are experiencing subsidence and severe flooding. The trapping of sediments behind dams constructed upstream from deltas constitutes another major threat to the long-term stability of deltas.

The future of the environment of planet earth has been a subject of extensive research because of the growing threat to the sustainability of the earth’s environment. In 2013, the International Association of Hydrological Sciences (IAHS) launched the “Future Earth” decadal research initiative, aimed at bringing together the environmental and social sciences to promote sustainable development. A 10-year “Global Delta Sustainability” initiative was declared the same year because deltas constitute important sub-sets of “Future Earth.” The goal of the Global Delta Sustainability initiative is to focus attention on the value and vulnerabilities of deltas worldwide, and to promote international and regional cooperation among scientists, policymakers, and other stakeholders.

Geology has always played an important role in the development of human society. Recently, Environmental Geology has emerged as a sub-discipline with a strong interdisciplinary approach (integrating other science disciplines, economics, law, etc.) to the understanding of geologic processes and the application of geological science to issues directly related to human activities. Environmental geology focuses attention on human interactions with earth processes, resources, and environment, and it identifies constraints imposed on human activities by geologic processes and vice versa. The key environmental geologic challenges, especially in urban delta areas are: increasing exposure of large human populations and infrastructures to geologic hazards (flooding, cyclones, etc.), provision of adequate and quality drinking water, safe waste disposal, contamination of soil, and water resources.

The restoration and maintenance of the sustainability of deltas require the development of integrated management strategies that incorporate extensive research, monitoring, and intensive consultation with the people whose activities are affecting and/or affected by deltas. The strongly interdisciplinary approach of Environmental Geology and its rapidly growing importance hold greater prospects for a better understanding of deltas as vulnerable, complex, socio-ecologic systems and ensures better preparedness in protecting, restoring, and mitigating them in a rapidly changing global environment.