Woolsey Fire Impacts on Coastal Water Quality in Southern California
Abstract
Coastal waters are hotspots of oceanic primary production that are extremely sensitive to changes in terrestrial and oceanic hydrology. As climate change progresses, wildfires are anticipated to increase in frequency and severity. Vegetation loss, reduced infiltration, and increased erosion in wildfire-impacted areas can significantly alter surface runoff from watersheds into coastal zones. Shifts in the turbidity of riverine discharges associated with wildfires alter sediment export to the coast, which in turn alters light and nutrient availability for organisms. In November 2018 the Woolsey Fire burned almost 100,000 acres in Ventura and Los Angeles counties, which are partially drained by Malibu Creek watershed. Following the fire, winter storms eroded burned areas flushing debris and sediment through the watershed into Pacific Ocean. Previous work has demonstrated increases in turbidity plume extents and fecal indicator bacteria levels in coastal waters following the Woolsey Fire. A Malibu Creek watershed SWAT model was used to quantitatively constrain changes in discharges and sediment fluxes from land to sea simulation between the years 2000-2020. A post-fire land cover map containing burned area land cover classes was generated from pre-fire land cover data modified using soil burn severity data. Parameters such as curve number were altered within the burned area land cover classes to reflect fire occurrence. The SWAT Land Use Update Tool was used to update land cover during the model simulation. SWAT model outputs, calibrated and validated using in situ observations of discharge and total suspended solids, will be used to assess and understand coastal ecosystem responses to wildfires.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMGC55H0328L