Measuring the Impact of Stream Restoration Activities on Redwood Forest Hydrology

Abstract:

The goal of this research is to understand how grade control structures installed in incised streams alter groundwater and surface water hydrology in a redwood forest located in Muir Woods National Monument, California. Muir Woods National Monument (Muir Woods) is a 224-hectare preserve of old growth redwood forest located in the Redwood Creek watershed. Most of Redwood Creek and its tributaries are incised as a result of historic channel modifications including removal of woody debris, and widespread rip rap installation. Channel incision of Redwood Creek and its tributaries has resulted in poor floodplain connectivity, limited channel migration, and altered channel morphology that collectively results in degraded riparian habitat and shifts in vegetation. In an effort to reverse channel incision and improve groundwater storage, the National Park Service is installing a series of rock check dams and densely packed vegetative debris on tributaries to Redwood Creek in a pilot restoration project. In this research we are using repeated terrestrial lidar surveys to measure changes in sediment storage and channel morphology where the grade control structures are installed. We are also monitoring groundwater to test the efficacy of the grade control structures at improving groundwater storage, which may provide substantial benefits to redwood forest ecology. The results of this project will inform future restoration efforts in Muir Woods and provide general insights into the dynamic connections between channel morphology and surface water-groundwater interactions in forested watersheds.