Modifying stream channels to control invasive species

Parts of the Laguna de Santa Rosa have become progressively shallower over the years as nutrient-rich sediment has washed downstream, slowed down and settled out. These wide, shallow, and sunny channels are suitable habitat for the invasive weed, Ludwigia hexapetala, which has completely overgrown parts of the Laguna. Sonoma Water plans to dig out sediment from the Laguna near Stony Point Road in Rohnert Park as part of their Water Quality Credit Trading Program. The digging project has resulted in a narrower, deeper, more shaded channel. We identified six study sites in the area that had sediment removed. At each site, we have characterized water depth, amount of canopy cover, and plant types present, and have gathered aerial images of each site using a drone. Moving forward, we will monitor these sites each semester to assess whether the new deeper channel design will prevent Ludwigia growth and improve habitat health.

Keywords: wetlands, transect survey, drone, Laguna de Santa Rosa