Benefits of Natural Floodplains & Open Space

Conservation & Floodplain Management

The tools and resources below apply broadly to land use and community planners, conservation and parks departments, elected officials, planning commission members, non-profits, and conservation organizations. The information, tools and links may assist the above entities in determining ways to incorporate species and habitat conservation into floodplain management strategies and decisions

Natural floodplains provide flood risk reduction benefits by slowing runoff and storing flood water. They also provide other benefits of considerable economic, social, and environmental value that are often overlooked when local land-use decisions are made.

Floodplains frequently contain wetlands and other important ecological areas which directly affect the quality of the local environment. Some of the benefits of floodplains to a functioning natural system include:

Fish and wildlife habitat protection
Natural flood and erosion control
Surface water quality maintenance
Groundwater recharge
Biological productivity
Higher quality recreational opportunities (fishing, bird watching, boating, etc.)

See the Green Guide, published by the Association of State Floodplain Managers, for more information on the benefits of natural systems and the history of floodplain development.

Natural Floodplains and Flood Loss Reduction

Floodplains provide numerous flood loss reduction benefits as a result of their unique natural functions. Rivers and streams shape floodplain topography and influence riparian habitats and riverine ecosystems. Likewise, the physical characteristics of the floodplain shape flood flows and can provide flood loss reduction benefits to include the following:

Excess water storage: Except in narrow, steep valleys and areas of coastal bluffs, floodplains provide a broad area which allows floodwaters to spread out and temporarily store excess water. This reduces flood peaks and velocities and the potential for erosion. Flood storage is particularly important in urban areas where even small floods resulting from a 5- or 10-year storm can cause severe flood damage. One acre of floodplain flooded one foot deep holds approximately 330,000 gallons of water.

Flow rate and erosion reduction: In their natural vegetated state, floodplains slow the rate at which the incoming overland flow reaches the main water body in the area. Vegetation also reduces shoreline erosion. In coastal areas, beaches, sand bars, dunes, and wetlands act as natural barriers to dissipate waves and protect back-lying areas from flooding and erosion.

Slowing runoff: A natural floodplain has surface conditions favoring local ponding and flood detention, plus subsurface conditions favoring infiltration and storage. Slowing runoff across the floodplain allows additional time for the runoff to infiltrate and recharge available groundwater aquifers when there is unused storage capacity. The slowing of runoff provides the additional benefit of natural purification of water as local runoff or overbank floodwater infiltrates and percolates through the floodplain alluvium.

Flow regulation during non-flood periods: During non-flood periods, groundwater discharge acts to naturally regulate the flow in a river or the level of a lake or pond.� In other words, during periods of abundant water, the water can enter the groundwater system whenever there is available capacity rather than contribute to seasonal flood peaks.� During low flow periods, the water flows from the higher groundwater system into lower surface waters, so that the frequency and duration of extremely low flows is reduced.

CRS – Protect Natural Floodplains

The CRS credits over 90 elements of comprehensive floodplain and watershed management that may be implemented by communities. The 90 elements include significant credits for protecting the natural functions of riverine and coastal floodplains, especially for

Preserving natural floodplain open space, and acquiring floodprone land and returning it to its natural state.
Planning for comprehensive floodplain management, including plans to protect and restore natural functions and habitat.
Watershed management programs, including those that identify wetlands and natural areas and help protect natural channels.

The CRS promotes comprehensive floodplain management planning, analysis and evaluation related to the protection of the natural functions of floodplains, and habitat protection. Credit is available for community-adopted management plans that protect and enhance one or more of the natural functions and native species of the local floodplain.

CRS communities earn flood insurance premium discounts for protecting the natural functions of floodplains by . . .

Preserving open space in floodplains;
Protecting natural shorelines;
Prohibiting fill in the floodplain;
Mapping natural floodplain functions;
Providing for low impact development, low density zoning, and land development criteria that encourage open space and floodplain protection;
Creating and implementing a watershed management plan, a habitat conservation plan, a natural functions plan, or a comprehensive floodplain management plan;
Prohibiting buildings in floodplains;
Regulations to protect natural and beneficial functions and water quality;
Management of stormwater;
Controlling erosion and sediment throughout the watershed;
Planning for the protection and restoration of habitat and the natural functions of floodplains;
Public outreach and education projects about the natural functions of floodprone areas;
Library collections about the local natural functions and resources, endangered, species, habitat, and other features;

Acquisition of floodprone properties and relocating them out of the floodplain;

Stream dumping regulations;
Erosion protection maintenance;

Link to Natural-Functions-and-CRS.

Learn about the benefits of protecting natural floodplain functions, including conservation of threatened and endangered species.

CRS Credit for Habitat Protection

An overview and guide to the ways communities can protect natural habitat while earning CRS credit. (Download .pdf)

Conserve Endangered Species

Identify where threatened and endangered species and critical habitat are located and learn more about those species and habitats.

Floodplain Buyouts: An Action Guide for Local Governments on How to Maximize Community Benefits, Habitat Connectivity, and Resilience

April 2017

This Action Guide is designed to help local governments across the country leverage hazard mitigation buyouts to protect, restore, and connect habitats in local communities. Greatly informed by the information gathered through in-depth case studies and conversations with key players in local buyout programs, the Guide highlights management approaches that will be useful and practicable for the local officials and managers who have the ability to target their acquisitions in ways that improve habitat connectivity and resilience while also reducing flood hazards.