FLOOD01659

• County: Statewide
• Title: Floodplain Management Handbook
• Date: 9/1/1981
• Prepared By: Flood Loss Reduction Associates
• Floodplain - Doc Type: Floodplain Report/Masterplan

Importance of Natural
Role of Floodplains

Floodplains play a vital role in
the interaction between land and water,
particularly with respect to moderation
of floods, maintenance of water quality
and recharge of groundwater. They are
particularly important in their undis-
turbed state because of the living
resources they support and the
environmental values they offer.

Moderation of Flooding

The characteristics of the flood-
plain and of flooding are closely
interdependent. Floods shape floodplain
topography, soils, and ecology. In
turn, the physical characteristics of
the floodplain shape flood flows.
Except for some steep valley and
coastal bluff situations, floodplains

provide a broad area to spread flood-
waters; thereby reducing veloc1ties and
lowering flood peaks. A part of the
flood is trapped and held back as it
. overflows' the floodplain by the
refilling of swamps and other wetlands,
and the temporary entrapment of water
in small depressions. These effects,
plus the meandering of streams, the
retardation of water by vegetation, and
other natural processes common to
undisturbed floodplains, reduce the
severity of downstream flooding.

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Floodplains along lake and ocean
shores serve a different function.
There the sloping beaches, barrier
islands, sandbars and wetlands absorb
the. energy of waves and protect the
landward area from excessive erosion.
Coastal dunes and shoreline vegetation,
such as some mangrove stands, also act
as a natural barrier to high waves and
storm surges.

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Floodplains are areas of great natural beauty and enormous biological produc-
tivity. Undeveloped floodplains reduce floods, improve water quality, aid
groundwater recharge and provide open space for recreation.

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