Wetlands are also susceptible to flooding when winter rains send fresh water to streams that feed into the Bay through them. The upper part of the mudflat is shallow enough to be exposed above water during low tides. Salt water enters the marsh through these channels during rising tides and drains through the channels during falling tides. When wetlands are destroyed, the Bay ecosystem loses much of its ability to support wildlife and environmental quality decreases. For example, wetlands provide habitat for diverse communities of plants and animals, are the principal habitat for migratory waterfowl, and absorb and filter pollutants that would otherwise degrade water quality.
Wetlands also dissipate fresh water flash floods, reducing their size and destructiveness.
You can observe that former tidal marshes and mudflats have been converted to salt ponds or diked for other uses. Many salt marshes around San Francisco Bay have been converted into housing and industrial developments. Some of these areas were originally diked for farmland, and then later used as building sites. However, projects in former baylands that are now behind dikes, and old projects that were underway at the time of the BCDC's creation, still present serious issues for appropriate use of the Bay's edge. This photograph is of Bel Marin Keys, a housing development along the northern edge of San Pablo Bay, near the mouth of the Petaluma River.