Sonoma Creek
The headwaters cut through gorge and meadow of Sugarloaf Ridge State Park, which boasts 25 miles (40 kilometers) of self-guided trails and the Robert Ferguson Observatory.In the 100 foot (30 m) deep gorge into which the waterfall spills is a moist mixed forest habitat including California bay laurel, coast redwood, Douglas fir, big leaf maple, cherry holly, coffeeberry, and even tanbark oak.The federally listed as threatened California red-legged frog is present in the northern reach draining the south slopes of Annadel State Park.Sonoma Ecology Center executive director Richard Dale reports that although beavers fell trees and dam culverts, on balance they perform nearly "perfect stream restoration," because they cause the creation of deep pools, slowing the flow of flood water and enhancing fishery habitat.Increased sedimentation has a variety of adverse impacts including direct harm to aquatic organisms and the more specific impact of altering streambed gravels to reduce productivity of spawning habitats; additionally sedimentation of pools decreases the efficacy of anadromous fish summering habitat by increasing critical summer water temperatures in these pools.The valley itself is part of the Franciscan Complex, which includes crumpled, uplifted terranes that have resulted from the subduction of the former oceanic Farallon Plate under the North American continent.This large marsh area has been reduced considerably from its historic dimensions due to construction of multiple levee systems and encroachment by agriculture and other forms of development.Historically the marsh supported an extremely diverse wetlands ecosystem, with a variety of primary productivity plants including pickleweed, eelgrass and giant bulrush (Scirpus californiens).As of 2006 this ecosystem has been significantly compromised by fill, levee formation, dredging and other development; estimates generally state that 75 percent of the original biological productivity of the marsh has been destroyed.Due to overpopulation of Sonoma Valley as well as overly intensive agriculture, groundwater supplies have been drawn down to the point of causing deleterious effects.[15] The U.S. Geological Survey has found in the Carneros region between Sonoma Creek and the Napa Ridge that due to excessive groundwater drawdown, saltwater intrusion is already occurring, rendering water unsuitable for many uses.