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Comparing channel form of restored tidal marshes to ancient marshes of the north San Francisco Bay

  • Author(s): Hall, Meredith
  • et al.
Abstract

In this study, I examine channel form in restored and natural tidal marshes to understand how marshes evolve from salt ponds and agricultural fi elds to naturally functioning tidal marshes. I examined the channel morphology of two marshes near the mouth of the Napa River in Solano County, California – one natural marsh approximately 100 years old (“centennial marsh”) and one restored in 1995 – using mapping techniques in ArcView GIS. I followed the techniques of a previous analysis done by Phil Williams and Associates (PWA) in 2003 on four other restored and natural marshes in the North San Francisco Bay and examined channel sinuosity, bifurcation ratios, length ratios, and drainage density (Garrity 2003). By combining my results with the results of the other four marshes, I have found that the data no longer fully conforms with the trends found by PWA. Both studies found that bifurcation ratios and length ratios of fi rst order channels tend to be larger for younger marshes. However, the contribution of my data shows that PWA’s observation that drainage density decreases with age is not entirely true. Instead, with the addition of data from the Napa centennial marsh, drainage density conforms more closely with the fi ndings of Steel and Pye (1997) that indicated drainage density increases with age up until about 150 years old and then decreases. Combining all of the data reveals that sinuosity tends to increase for 2nd order channels with the age of the marsh.

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