Stream Care Guide:

Management Tips for Streamside Property Owners

Flooding

The best way to avoid flood problems is to find out where the floodplain is and don't build there!

If you already have developed land in the floodplain of a small stream, you may be able to reduce the frequency or extent of flooding. It may take a joint effort of you and your riparian neighbors.

Any structure built within the reach of flood waters is not only subject to damage or loss but may actually decrease the stream's ability to safely accommodate floods by removing protective vegetation and destabilizing vulnerable slopes. In keeping with the value of the riparian zone, avoid building any structure there — even decks or patios.

Residential and commercial development has increased storm runoff in many areas, raising the risk of flooding. Creekside structures are thus likely to become more vulnerable over time, not less so. Recognizing this flood hazard, county ordinances regulate all building in the flood plain. The safest advice, for your property and your stream, is to maintain the flood zone in its natural state.

If flooding is a problem, don't do anything that will reduce the amount of water the stream channel can carry above, through, and below your property (channel capacity). Constrictions in the channel slow the water down and cause it to back up and rise to higher levels than it would otherwise. Examples of constrictions are undersized culverts, retaining walls built out into the creek, clogged and overgrown vegetation, and large debris jams. Anything that takes up a lot of space in the channel may aggravate flood problems.

In Figure 1 (below), the channel was enlarged before the bank protection was installed. In Figure 2, the retaining walls have reduced the width of the stream channel.

Figure 1

Figure 2

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