The Sediment Dichotomy
A combination of eroding soils, landslides and debris flows, and incising and widening channels annually supply large volumes of sediment to the Creek. Coarse sediment is positive for the creek segments managed for spawning and rearing habitat for salmonids. However, those same coarse sediments can fill reservoirs and the downstream flood control channel in Fremont, impact bridges, and impair regular operation and maintenance of groundwater pumping and percolation facilities. Fine sediment is generally deleterious to all the beneficial uses of the Creek. However, once both types of sediment have passed through the flood control channel and into the Bay, they are valuable as the supply for the biological and physical material necessary for wetlands on the Bay margin. Hence, agencies managing different parts of the Creek system face a dichotomy of competing needs with regards to coarse and fine sediment.
Developing Information and Coordination among Groups
Agencies, stakeholders, and land owners have begun the process of learning about where sediment comes from, what kinds of sediment are in the Creek (coarse versus fine), what measures may be affective to protect channels, how it moves through the system, how it collects behind structures and in channels, and how much of it moves through to the wetlands on the Bay margin. Presently, much of this information is being collected in isolation by agencies in response to their individual needs and goals. However, due to a common regulatory framework, there are likely instances where sharing information or perhaps even developing joint monitoring, research, or modeling projects would reduce overall costs and increase the usefulness of the information generated.
