Flood Characterization in Pacific Northwest Coastal Mountains

Abstract:

In coastal mountains relative contributions of hydrometeorological (rain, snow, and glacial melt) and geomorphic factors (sediment deposition, channel change) control flooding. Understanding the relative contributions of these factors to flood generation is critical to improving flood modeling and therefore ensure resilience to flooding. The Puyallup River Basin located in the Pacific Northwest region provides an excellent domain for such flood anatomy given its complex terrain (glaciated stratovolcano), land cover and land use, and climate conditions. We examined and characterized the recent floods in Puyallup River Basin by investigating flood processes in representative sub-basins of different altitude, drainage area, steepness, and dominant conditions of hydrometeorological and geomorphic processes. Through the investigation and the comparison of flood properties along with their associated meteorological, hydrological, and channel characteristics, we gain knowledge of the spatial and temporal characteristics of flood formation and how it scales through the stream network. Results also help identify basin geomorphic attributes such as how landscape functions in transporting major geomorphic processes. The detailed flood anatomy will better inform decision makers on improving flood resilience in the PNW region.