Vegetation Loss in the California Highway 37 Strip Marsh

Name: Vegetation Loss in the California Highway 37 Strip Marsh
Creator: California State Geoportal
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California State Geoportal2026-03-28 收录

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https://gis.data.ca.gov/maps/c8c04dbe85dd419b8ae685a6ad04e391

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Watershed Stewards Program (WSP) Corpsmembers and Scientists from the SF Bay Regional Water Quality Control Board created this StoryMap to visually demonstrate and roughly quantify the change in vegetation within the Highway 37 strip marsh over the last two decades. The purpose of this StoryMap is to illustrate the current trajectory of vegetation in the strip marsh and inform decision makers in their planning efforts. The Highway 37 strip marsh is a wave-built platform of high tidal marsh located along Highway 37 between Tubbs Island and Mare Island in the Napa-Sonoma Marshes. Because the strip marsh grew bayward over time, the innermost (northern) portions of it formed when sea levels in the San Francisco Estuary were lower; therefore the marsh acts like a bowl that floods during high wave/water events but subsequently drains slowly, if at all. Over the past 20 years, extended periods of inundation in the inner marsh east of the Pond 1/1A intake channel have caused the marsh’s formerly dense stands of pickleweed (Sarcocornia pacifica) to drown, exposing extensive mudflats, driving periodic dust storms on Hwy 37, and resulting in the significant loss of habitat for multiple species including the federally endangered salt marsh harvest mouse (Reithrodontomys raviventris). In addition, after being relatively stable for decades, the strip marsh’s bayward edge (scarp) has been eroding landward since roughly 2010, which creates the potential for catastrophic collapse of the marsh platform should scarp retreat continue and intercept the de-vegetated inner flats.In order to demonstrate this change in vegetation, our team quantified the difference in the Normalized Difference Vegetation Index (NDVI) across 20 years in the strip marsh. Over this time period, the estimated area of de-vegetated strip marsh increased from 6% to 37%. Data was sourced from publicly available USGS Landsat 5 and Landsat 8 imagery. With the assistance of scientists at the USGS, this remote sensing technique was verified as an effective method of measuring non-vegetated reaches of wetlands. Landsat NDVI imagery was also verified against higher resolution USDA NAIP imagery. To use this StoryMap, simply scroll down the application. The slider function of the main graphic can be dragged left to right to show the difference in vegetation between 2001 and 2021. The maps are interactive and can be zoomed into for a more detailed view.This content was created by Christina Toms, Jamal Jaffer, and Jacqueline Hewitt from the San Francisco Bay Regional Water Quality Control Board, Planning Division. christina.toms@waterboards.ca.gov, jamal.jaffer@waterboards.ca.gov, jacqueline.hewitt@waterboards.ca.gov

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California State Geoportal