Increased Sediment Loadings into Coastal Waters Following Wildfire: A
Remote Sensing and Modeling Perspective
Abstract
Coastal watersheds impacted by wildfires experience increased sediment
delivery to the ocean that alter the availability of limiting factors
(i.e., light) for marine organisms. With increasing wildfire magnitude
and severity, it is critical to explore changes in riverine discharges
to the ocean to assess cascading hazards associated with wildfires. In
situ data and a hydrological model adapted to capture fire-related land
use change are paired with remotely sensed turbidity data to investigate
Woolsey Fire impacts on Malibu Creek, California, USA. Maximum post-fire
observed and simulated discharges and sediment loads were between 1.4 –
4.8 and 0.93 – 13.9 times higher, respectively, than during non-fire
periods with similar rainfall. Mean turbidity also increased to 18.2
Formazin Nephelometric Unit (FNU) during the first storm post-fire (mean
background value of 4.3 FNU). Synergies between the methods were able to
better characterize post-fire sediment fluxes versus a single method.
Notably, remote sensing observations captured rapid coastal sediment
exports within the first post-fire month that SWAT did not. Conversely,
sporadic remote sensing observations did not reflect ongoing post-fire
sediment erosion (largely due to cloud cover issues), which SWAT did
demonstrate. These data are essential to understanding fire-related
marine ecological changes and implementing effective management and
conservation initiatives.