Floodplains
A floodplain is an area next to a river, stream, or creek that may be covered with water following heavy rainstorms. This plain holds the excess water allowing it to be slowly released into the river system and seep into groundwater aquifers. Floodplains also give time for sediment to settle out of floodwaters, thereby keeping it out of water bodies. Floodplains often support important wildlife habitat and are frequently used by humans as recreation areas.
In the past, building development has occurred on the floodplains, which required trying to control the stormwater to keep it out of the floodplains. This practice causes water to overflow riverbanks in other locations – often creating floods of a greater magnitude and danger.
Building on floodplains increases the risk of property damage and life threatening situations. Diverting stormwater into channels and easing its path to bodies of surface water forces water to flow faster. This greater velocity destroys habitats and causes greater erosion including the loss of topsoil which often creates a need for increased fertilizer use.
What are some other factors that affect flooding?
- Erecting structures that deflect or inhibit the flow of floodwaters. This modifies flow paths and can spread flooding problems and increase erosion.
- Constructing bridges, culverts, buildings, and other structures that encroach on the floodplain. These developments reduce the storage area available for floodwaters and cause an increase in flood elevations.
- Building drainage systems that feed stormwater quickly into the receiving body.
- Straightening meandering watercourses to hasten drainage. This transfers flooding problems downstream and also alters habitat.
- Filling and dumping in floodplains. Floodwaters can transport this debris, which may interfere with the movement of the floodwater, causing increased flood elevations.
- With increasing development in the floodplain, open spaces, and wetlands, our land has lost the ability to soak up rain. Areas that were once effective sponges storing precipitation are now being replaced by buildings and pavement that have made the land increasingly impervious. As a result, floods have become far larger and frequent. Local governments can prohibit building in the floodplain.
How can we prevent flooding?
Taking the time to word your community’s zoning ordinances so that they reflect the importance of preserving water quality is an important task. There are many angles to do this from including:
- Stormwater Control Ordinances
- Floodplain regulations
- Impervious Surface Restrictions
- Shoreline Vegetation Cover Restrictions
- Building and Septic field setbacks
The following are things to think about adding to your zoning ordinances:
- Prohibit construction of buildings and facilities subject to water damage in the 100-yr floodplain.
- Require flood-proofing measures on buildings presently in the floodplain.
- Remove flood-prone structures from floodwater portion of the floodplain.
- Establish construction standards for development in the floodplain.
- Adopt provisions to protect natural vegetative cover the in floodplains.
- Require tree and shrub planting in the floodplains to prevent erosion.
- Restrict dredging, filling, dumping, or backfilling of floodplain areas.
- Avoid land divisions within floodplain areas that would create parcels or lots that cannot be used.
- Require that flood insurance be obtained for all facilities in floodplain under National Flood Insurance program.
- Require that before local approval can be granted, a permit must be secured from the MDNR.
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