Floodplains and environmental threats
Floodplains are low-lying areas adjacent to river channels that become inundated when rivers overflow, playing a crucial role in various ecosystems, especially in humid and tropical regions. They are known for their rich biodiversity, providing habitats for numerous aquatic and terrestrial species, and are often fertile grounds for agriculture, allowing for the cultivation of crops like rice and timber harvesting. However, floodplains face significant environmental threats, particularly due to climate change, which leads to increased flooding and land subsidence in some areas. Urbanization further compounds these issues by altering natural water flow and introducing pollutants that degrade water quality and disrupt local ecosystems. Human activities such as deforestation, construction, and land development can exacerbate flooding and diminish the ecological health of floodplain areas. As global warming progresses, communities located in flood-prone regions may find their environments increasingly uninhabitable, necessitating an integrated approach to floodplain management to mitigate these risks. Understanding the delicate balance of floodplain ecosystems is vital for preserving their ecological integrity and supporting the communities that rely on them.
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Subject Terms
Floodplains and environmental threats
DEFINITION: Low-lying areas adjacent to river channels that become partially or completely covered with water when the rivers overflow their banks
Floodplains occupy an important part of landforms around rivers covering large areas, especially within humid and tropical climatic settings. They also house riparian wetlands, acting as buffers to flooding. Floodplains provide habitat for many land and aquatic life-forms.
Floodplains filter water and provide and nutrients that make them fertile places. Perhaps the most famous examples are the fertile floodplains of Egypt’s Nile Valley region, which have supported civilizations for several millennia. Floodplains also provide and backwaters to wetlands, and they also dilute salts, thereby improving the health of the for fish, bird, and plant populations that inhabit the floodplains.
Floodplains are good for food production such as rice cultivation. Farmers graze their livestock on the grasslands in floodplains, and fresh fruits and cash crops are grown in floodplains, which are often very fertile and easy to cultivate. In tropical settings, timber is harvested on floodplains, and non-timber forest resources such as animals and plants are used for foods and medicines as well as construction materials.
Types and
Riverine flooding can cover vast areas, many of which are among the most diverse biologically productive ecosystems on earth. Three types of floodplains are identified based on temperature: temperate stochastic, temperate seasonal, and tropical seasonal. Within floodplains, appear to provide the most important source of primary production within the grazer web. The flow regime is very important in determining the physical habitat for biotic composition. The shape, size, and the formation of features such as deltas, riffles, runs, pools, and backwaters that tend to shift are linked to the flow regimes of rivers. Certain aquatic life-forms have their early life stages in floodplains, and the types of fauna and flora within floodplains can be as diverse as in any other ecosystems. Owing to the highly dynamic nature of terrains, varied species may be seen on the same floodplains over the course of years.
Floodplains contain several kinds of geomorphologic features, including oxbow lakes, point bars, areas of dead water, and braided channels. Swamps, among other types of riparian wetlands, can also be found in floodplains. Floodplains can be classified into different types depending on their morphology. Several methods of classification are used, but the simplest and most common is based on the fluvial styles: gravel-dominated, sand-dominated with high sinuosity, and sand-dominated with low sinuosity.
Environmental Threats
As global warming increases, some floodplains may see more flooding, which will greatly affect local populations because of land subsidence and increases in water level. For example, in the beginning of the twenty-first century, Bangkok, the capital of Thailand, was at a rate of 2 to 3 centimeters (0.79 to 1.18 inches) per year because of sediment compression and owing to increased human activities. The elevation of New Orleans, Louisiana, continued to drop in 2023, at a rate of about 5 centimeters per year, with one neighborhood, Village de L’Est, topping out at a sinking rate of 2.54 centimeters (1.5 inches) per year.
Urbanization affects the of floodplains, either by reducing water through withdrawal or by adding to it through importation. It also alters the water chemistry by introducing chemicals, sediments, and other forms of pollutants, including increases in temperature, all of which affect the biotic richness of floodplains. The nutrients brought into play through flood activities can also be altered through changes in land-use patterns. Changes within a (watershed) affect the production and supply of materials in floodplains. High levels of can provide stability to floodplain ecosystems and help protect them from human-caused impairments.
The expansion of urban areas into floodplains and alters the onset, duration, distribution, speed, quantity, and quality of floodwaters. Among the human activities that lead to increases in flooding are and the removal of stabilizing vegetation along riverbanks. Human-built structures along or near rivers affect the flow direction, resulting in deflection of the water, or reduced storage. Storm drains, housing developments, and pavements increase the rate of rainfall to rivers, thereby increasing the rate of flooding. The straightening of river channels increases the rate at which water is transported. Another human activity that affects floodplains is the dumping of sediment loads from farms or construction sites into rivers, which decreases channel depth and increases the area covered by floodwaters. With increasing changes in land use, a approach to floodplain management becomes imperative.
Impairment of floodplain waters can have adverse effects on coastal ecosystems, as these waters end up in lakes or oceans. The quality of the water in rivers has a great impact on the quality of the water in nearby coastal areas; the waters of the Amazon, for example, can be traced several miles into the Atlantic Ocean. Contaminants carried in such waters ultimately affect large biological populations.
Global climate change is expanding the areas classified as floodplains. Many densely populated coastal communities, for example, occupy sites that are expected to be underwater or so frequently flooded in the future that they will not be habitable.
Bibliography
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