How does the floodplain of a river develop

Giving rivers room to move is our best protection against floods and is a great way to help keep rivers healthy. Heavy rains over a short period of time can suddenly cause a flood. Or, lighter rains falling over many days or weeks build up, eventually causing the river to overflow.

Natural rivers have small floods nearly every year, usually during the rainy season. During these seasonal floods, water spreads over riverside floodplains and creates seasonal wetlands that provide critical habitat for fish and birds.

Some rivers completely transform between rainy and dry seasons. These small, frequent floods are an integral part of a healthy river.

Many people think that all floods are bad. Small floods are, in fact, essential to the health of rivers. This water can be stored and used by nature and people. They also filter pollutants out of rivers and nourishing lands to support ecosystems and fertile areas for farming. Flooding creates islands and channels and other habitat that are home to fish, birds, and other wildlife.

And while they do that, floods also help flush out invasive plants and animals, benefitting native species. The reproductive cycle of many species relies on flooding to start. For example, a number of fish, such as the sturgeon, and plants such as the willow tree. Very large floods occur much less often. They cause the river to spread out across a larger area, threatening homes and businesses constructed in the floodplain.

Floodplains are actually a part of the river. They nurture life and naturally protect us from floods. When a river floods, water spreads across the floodplain and slows down. Without floodplains, rivers would rise and move faster, just as water from a hose moves faster when you hold your finger over part of the opening. Floodplains act as natural filters, absorbing harmful chemicals and other pollution, making rivers healthier for drinking and swimming, and for plants and animals.

This can help prevent floodwaters from reaching homes and businesses. They are our first and best defense against flood damage. Rivers deposit sediment and nutrients in floodplains, making them very productive areas for growing crops. Floodplains are a productive environment for plants and wildlife and serve as nurseries for many species of fish. They provide vital habitat and are important for maintaining the web of life.

These are ideal places for hiking, paddling, fishing, exercising, and connecting with the beauty of nature. During floods, water can replenish groundwater supplies. Capturing flood water during wet years is one of the best ways to ensure adequate groundwater during droughts. For many decades, communities have built structures such as dams and levees linear earthen berms built alongside a river to keep flood water from damaging homes and businesses built on floodplains.

These man-made structures age and are not always effective against the largest floods. On top of that, these structures disconnect rivers from their floodplains, causing harm to wildlife and fish and eliminating any benefits that natural floodplains provide to people and communities. These structures can be overwhelmed by large floods. When the river floods, the sediment spreads out across the floodplain.

When a flood occurs, the river loses energy. The largest material is deposited first on the sides of the river banks and smaller material further away. After many floods, the sediment builds up to increase the height of the river banks, meaning that the channel can carry more water a greater discharge and flooding is less likely to occur in the future.

Estuaries An estuary is where the river meets the sea. An estuary and its mudflats. Additionally, once waters have spread out on to the floodplain, water flow is slowed and has more time to seep into the ground where it can replenish aquifers, which serve as a primary source of water for many communities.

Floodplains also play a vitally important role in supporting the broader ecological health of the watersheds in which they are found. Thanks in part to the natural flooding process, floodplains are home to some of the most biologically rich habitats on Earth, providing spawning grounds for fish and critical areas of rest and foraging for migrating waterfowl and birds. Many of these species that rely upon naturally functioning floodplains are also commercially or recreationally important, thus providing the underpinnings for local economies built around the multibillion dollar outdoor recreational industry.

Activities like fishing, hunting, camping, hiking, wildlife watching and boating are all dependent on the natural processes of rivers and healthy floodplains and the groundwork they provide for healthy ecosystems. The report lays out the benefits of floodplains as well as challenges that they are facing and includes recommendations from the taskforce and a set of case studies. The Association of State Floodplain Managers has a wide array of resources regarding floodplains on their website. FEMA has compiled guidance on floodplain management.

Rivers, Streams, and Floodplains Floodplains are the areas of low-lying ground adjacent to rivers, formed mainly of nutrient-rich river sediments and subject to flooding after storms and heavy snowmelt.

Hazard Mitigation During floods, floodplains essentially increase the ability of a river to move or convey floodwaters.