Publication Date
Fall 2024
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Geology
Advisor
Emmanuel Gabet; Daniel Malmon; Scott Hamilton
Abstract
In 2021, the lower Mill Creek Dam (~4 m tall, ~8 m wide) was removed from the Mill Creek-San Vicente Creek watershed (18 km2), located in the Santa Cruz Mountains. Topographic surveys and pebble counts were performed at 27 transects four times between 2021 and 2023 to compare changes in channel characteristics and grain size to document the response to a small dam removal and the transition between drought and flood conditions. The goals of this study were to: (1) describe the movement of impounded sediment; (2) assess the success of habitat restoration for two endangered anadromous fish species: coho salmon (Oncorhynchus kisutch) and steelhead trout (Oncorhynchus mykiss); and (3) evaluate the impact of drought deluge conditions on a dam removal in a small coastal watershed. The dam removal initiated a rapid period of channel widening and incision upstream until reaching a stable base level, releasing an initial pulse of impounded sediment, which moved downstream through the process of dispersion and change in slope influenced the sediment distribution. The flood event in 2023 renewed channel widening and incision and the high flows removed fine sediment (< 2 mm) which accumulated during the drought. The combination of the dam removal and flood event improved habitat conditions as optimal spawning gravel replaced fine sediment downstream. This study contributes to ongoing research on the effects of dam removals in small coastal watersheds as they experience more frequent and severe weather fluctuations.
Recommended Citation
Doyle, Madeline C., "Assessing Sediment Migration and Salmonid Habitat Recovery Following a Small Dam Removal and a Flood, Mill Creek, California, Usa" (2024). Master's Theses. 5590.
DOI: https://doi.org/10.31979/etd.bgvj-wxdg
https://scholarworks.sjsu.edu/etd_theses/5590
