Quantifying current and future floodplain habitat for coho salmon (oncorhynchus kisutch) in Lagunitas Creek (Marin County, CA)

The coho salmon (Oncorhynchus kisutch) Central California Coast evolutionary significant unit (CCCESU) has declined from an estimated 50,000-125,000 adult returns to only 500 spawning adults, and is at high risk for extinction. Lagunitas Creek (Marin County, CA) supports 10% of the remaining population, but much of the watershed has incised stream banks and disconnected floodplains. Previous studies have implicated overwintering habitat for juveniles as a limiting factor and the priority for restoration efforts. Good overwintering habitat is characterized by complex channel form, refugia from predators, connected floodplains, and riparian vegetation. I used data derived from Light Detection and Ranging (LIDAR) to compare the floodplain height above river (HAR), vegetation height, and plant community type attributes in areas of Lagunitas Creek where coho juveniles are successfully overwintering and areas with poor smolt production. I found that 72.2% of the Lagunitas floodplain is five meters or less above base flow, comprised of 24.2% lower (0-2m) and 47.9% upper (2-5m) floodplain. The Tocaloma reach supported the most lower floodplain habitat, while the Point-Reyes-Nicasio reach had the greatest amount of upper floodplain My results, linking the floodplain elevation attributes to the plant height and community type, suggest many sections of the Lagunitas Creek can be restored as overwintering habitat for coho salmon.