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California Clapper Rail cont. be imported to increase the elevation. Since materials are brought in as wet mud, they will eventually dry and settle. Unfortunately, the amount of settling is sometimes unpredictable. If the mud settles too much, the restored area will be too low for marsh vegetation and may require additional materials. However, if the mud doesn't settle as much as predicted, the area will be too high and dry for growth of healthy marsh vegetation and formation of tidal channels. Another major issue associated with dredge spoils is that they may contain high levels of certain contaminants, which would make them unsuitable for use in wetlands restoration projects. Opening restoration areas to tidal action allows sedimentation and formation of marshes to occur, although at a slower rate than with dredge spoils. Since the sediment load in San Francisco Bay is quite high, enough sediment is present in the water column to allow the elevation of restoration areas to increase quite rapidly up to a level that will support marsh vegetation. The advantage of this method is that it allows tidal channels to form naturally, which will result in the formation of a relatively healthy, self-sustaining marsh with sufficient tidal action to support vegetation. Depending on sedimentation rates and initial elevation of the restoration area, sedimentation may take approximately 5-15 years before marsh vegetation begins to grow. If rail habitat requirements are taken into account when planning habitat restoration, more successful rail recovery may be possible. However, the process of marsh restoration is still in the experimental stage and we have not yet discovered how to recreate marshes as good as those created naturally. Therefore, monitoring the success of restoration projects is critically important, because it is our only chance to learn how to improve our methods. There are many current marsh restoration projects in the San Francisco Bay area. The San Francisco Bay National Wildlife Refuge Complex is involved in several, including restoration of a 1,500 acre parcel of former farmland, called the Napa Marsh Unit (formerly known as Cullinan Ranch), in the Napa |
Last updated:
May 22, 2008
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