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Environmental Geology and Sustainability of Deltas  

Enuvie G. Akpokodje

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.

Article

Urban Heat Islands and Their Associated Impacts on Health  

Clare Heaviside

Towns and cities generally exhibit higher temperatures than rural areas for a number of reasons, including the effect that urban materials have on the natural balance of incoming and outgoing energy at the surface level, the shape and geometry of buildings, and the impact of anthropogenic heating. This localized heating means that towns and cities are often described as urban heat islands (UHIs). Urbanized areas modify local temperatures, but also other meteorological variables such as wind speed and direction and rainfall patterns. The magnitude of the UHI for a given town or city tends to scale with the size of population, although smaller towns of just thousands of inhabitants can have an appreciable UHI effect. The UHI “intensity” (the difference in temperature between a city center and a rural reference point outside the city) is on the order of a few degrees Celsius on average, but can peak at as much as 10°C in larger cities, given the right conditions. UHIs tend to be enhanced during heatwaves, when there is lots of sunshine and a lack of wind to provide ventilation and disperse the warm air. The UHI is most pronounced at night, when rural areas tend to be cooler than cities and urban materials radiate the energy they have stored during the day into the local atmosphere. As well as affecting local weather patterns and interacting with local air pollution, the UHI can directly affect health through heat exposure, which can exacerbate minor illnesses, affect occupational performance, or increase the risk of hospitalization and even death. Urban populations can face serious risks to health during heatwaves whereby the heat associated with the UHI contributes additional warming. Heat-related health risks are likely to increase in future against a background of climate change and increasing urbanization throughout much of the world. However, there are ways to reduce urban temperatures and avoid some of the health impacts of the UHI through behavioral changes, modification of buildings, or by urban scale interventions. It is important to understand the physical properties of the UHI and its impact on health to evaluate the potential for interventions to reduce heat-related impacts.