Ledson Marsh Restoration: Annadel State Park

Abstract:

This project will stabilize and restore the Ledson Marsh dam, ensuring the survival of this important 30-acre marsh ecosystem and the wildlife that depend on it.  The dam is currently in a severely degraded state, and in desperate need of repair.  This project will correct the current erosion occurring from the dam as it deteriorates, and rebuild the dam so that it functions properly to sustain the hydrology of the seasonal wetland.  This project is critical for the survival of the population of California Red-legged Frogs that live in Ledson Marsh.

Purpose: This project is located at Annadel State Park, Sonoma County, between Highway 12 in the Sonoma Valley and Highway 101. Annadel is the major landbase within the Sonoma Valley where over 300,000 trails users recreate annually. The project is located at Ledson Marsh, home to one of the most significant populations of the federally-threatened California Red-legged Frog in Northern California. The project site, Ledson Marsh, is a 30-acre freshwater wetland, and is also used extensively by waterbirds and shorebirds for foraging and nesting. Purpose: This project will stabilize the marsh's six-foot tall earthen dam. The Ledson Marsh Dam was constructed in 1930 by a former private landowner. During the ensuing years the reservoir area impounded by dam has developed into a marsh that has become a valuable wildlife habitat. However, the dam has deteriorated and now leaks resulting in a seasonal water level pattern of full reservoir during winter and spring, and a gradually lowering water level during the summer and near fully drained condition in the fall. This project aims to repair the dam for long-term stability, utilizing a design that would allow for water to drain slowly from the marsh during summer, drying the marsh out by fall. This hydrologic pattern is important to promote California Red-legged Frog populations while also preventing bullfrogs from becoming established. If the marsh does not dry out annually, bullfrogs can persist in the marsh, threatening native amphibian populations. There is now a concern for the dam's safety, but also a desire to maintain the present annual cycle of marsh water lelvels in order to maintain the habitat. Need: DPR must strike the delicate balance between public safety, habitat enhancement and resource protection. As the condition of the dam continues to deteriorate, concern for the public and downstream homeowners increases. Catastrophic dam failure would cause flooding in the Schultz Creek drainage where several homes are located outside park boundaries. In addition to the safety concern, this project is needed to ensure the survival of the California Red-legged frogs and other wildlife species that depend on the marsh ecosystem.

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Watersed Management Strategies:

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