Event Title
Modeling the effects of climate change on peak flows in the Nooksack River, North Cascades, WA
Presentation Abstract
The Nooksack River in northwest Washington State provides freshwater for agriculture and industrial use and serves as a vital habitat for endangered salmon, a resource that is of cultural and economic importance to the Nooksack Indian Tribe. Historically, peak streamflows in the 2300 sq-km Nooksack basin are driven by rainfall in the fall and early winter. Global climate models (GCMs) project an increase in air temperatures for the Salish Sea region, and previous modeling within the Nooksack basin projects a reduction in snowpack extent through the 21st century and an increase in winter streamflow magnitude. As more landscape becomes exposed to rain rather than snow in the winter, peak flows and sediment delivery to streams will increase due to rapid runoff, resulting in salmon habitat degradation and increased flood risk. To quantify the timing and magnitude of future peak flows, we use the Distributed Hydrology Soil Vegetation Model (DHSVM) with a 150-meter grid spacing and new historical and projected meteorological data at a 6-km resolution produced with the Weather Research and Forecasting (WRF) model at 1-hr time steps. The DHSVM was calibrated to stream discharge from four USGS stream gauges and snow-water equivalent from three SNOTEL sites within the basin. We used the calibrated model to simulate 12 high emission GCM scenarios (i.e., Representative Concentration Pathway 8.5) through 2099 that were dynamically downscaled with the WRF model. Dynamical downscaling offers a way of increasing the temporal resolution of forcings, specifically the intense rainfall events that drive flooding in western Washington. Results indicate an increase in the frequency of winter stream peak flows and a 25% average increase in winter peak flow magnitudes by the end of the 21st century, increasing the risk to lowland infrastructure and salmon restoration efforts.
Session Title
Integrating Climate Science into Flood Plain Management
Conference Track
SSE8: Climate Change
Conference Name
Salish Sea Ecosystem Conference (2022 : Online)
Document Type
Event
SSEC Identifier
SSE-traditionals-332
Start Date
27-4-2022 1:30 PM
End Date
27-4-2022 3:00 PM
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Modeling the effects of climate change on peak flows in the Nooksack River, North Cascades, WA
The Nooksack River in northwest Washington State provides freshwater for agriculture and industrial use and serves as a vital habitat for endangered salmon, a resource that is of cultural and economic importance to the Nooksack Indian Tribe. Historically, peak streamflows in the 2300 sq-km Nooksack basin are driven by rainfall in the fall and early winter. Global climate models (GCMs) project an increase in air temperatures for the Salish Sea region, and previous modeling within the Nooksack basin projects a reduction in snowpack extent through the 21st century and an increase in winter streamflow magnitude. As more landscape becomes exposed to rain rather than snow in the winter, peak flows and sediment delivery to streams will increase due to rapid runoff, resulting in salmon habitat degradation and increased flood risk. To quantify the timing and magnitude of future peak flows, we use the Distributed Hydrology Soil Vegetation Model (DHSVM) with a 150-meter grid spacing and new historical and projected meteorological data at a 6-km resolution produced with the Weather Research and Forecasting (WRF) model at 1-hr time steps. The DHSVM was calibrated to stream discharge from four USGS stream gauges and snow-water equivalent from three SNOTEL sites within the basin. We used the calibrated model to simulate 12 high emission GCM scenarios (i.e., Representative Concentration Pathway 8.5) through 2099 that were dynamically downscaled with the WRF model. Dynamical downscaling offers a way of increasing the temporal resolution of forcings, specifically the intense rainfall events that drive flooding in western Washington. Results indicate an increase in the frequency of winter stream peak flows and a 25% average increase in winter peak flow magnitudes by the end of the 21st century, increasing the risk to lowland infrastructure and salmon restoration efforts.
