Recharging water sources: Floods are natural hydrologic processes and provide variable river flows and are an intermittent source of freshwater supply, filling natural depressions and recharging groundwater. Inundation of the flood plains helps recharge the groundwater, which is an important source of drinking water and is essential for agriculture. They are an important source for restocking local man-made water sources such as ponds, reservoirs, dams and irrigation channels, meeting round-the-year demand.
Agriculture: Floodwaters carry nutrients and sediments, which are deposited on flood plains, enriching the soil.. Rice paddies are flooded deliberately to take advantage of this natural fertilization process.
Fishery: A river basin is an ecological unit interconnecting upstream spawning habitats with downstream rearing habitats for a variety of species and other aquatic systems. Seasonal habitats on the flood plain, created by variable flow regimes, are essential for various stages of the life cycle of species. Floods provide an ecological trigger for both the spawning and migration of certain species. Some species spawn on the flood plain itself, whereas others migrate upstream to spawn in the river channel, providing an abundant supply of fish and alternative income sources at the household level.8
Rejuvenation of the river ecosystem: The river ecosystem is a critical habitat for the biota: fish, wildlife and waterfowl. Seasonal variability and variable sediment and flow regimes help maintain ecological biodiversity in rivers and flood plains. Wetlands or swamps located in flood plains serve as natural buffer zones for excessive flood flows and play host to many birds, fish and plants. Supplementary livelihoods in the form of recreational and eco-tourism activities can be made possible by the presence of the rich river ecosystem, bestowed with abundant flora and fauna. Surface runoff and flooding can help wash down pollutants and contaminants deposited on land caused by the intensive use of pesticides and fertilizers. They also flush out accumulated organic substances brought by untreated drainage water from farmlands, stockyards, factories and domestic use and restore the ecological health of stagnant rivers and streams by diluting them and providing clean water.
For more information about the river ecosystem, please refer to “Environmental Aspects of Integrated Flood management“, Section2.3.