PREEVENTS TRACK 2: Integrated Modeling of Hydro-Geomorphic Hazards: Floods, Landslides and Sediment

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Floods claim many lives, destroy property, and cost billions of dollars annually, motivating the need for improved tools for making predictions. Flooding is typically related to higher precipitation, but there is growing evidence that reduction of a river channel's ability to convey floodwaters as a result of sediment deposition can lead to more frequent floods and increased flood hazards. Current flood models do not sufficiently resolve sediment dynamics in river networks and related consequences for channel conveyance. The overarching objective of this research is to improve our understanding and ability to forecast flood and landslide risks by targeting key uncertainties of sediment inputs to the system from landslides and debris flows and sediment dynamics in channels. The investigators will develop process-based models, which will be directly compared with existing operational flood models, so that advancements and innovations at the research level can be moved toward operational models rapidly. Two PhD students and two postdoctoral associates will receive training with faculty and government scientist support in a multi-disciplinary research environment. This project will use Landlab, a recently developed toolkit for modeling earth surface processes, to model upland sediment input and sediment dynamics in channel networks. Landlab will be incorporated into an integrated flood modeling framework that includes distributed hydrology (DHSVM), and fluvial geomorphology and hydrodynamics (Delft3D) models. DHSVM will provide hydrologic forcing to Landlab, which will be used to model sediment flux that is routed through the watershed by DHSVM and incorporated into Delft3D for flood prediction. This modeling framework will be applied to Skagit and Puyallup Rivers draining two different sediment-laden stratovolcanos, Glacier Peak and Mount Rainier, in the State of Washington. The Skagit and Puyallup Rivers both have long histories of generating damaging floods linked to sedimentation processes. The modeling framework will be extensively validated with existing observations and remote sensing data to address the following questions: (1) What are the dominant geomorphic processes that lead to sediment supply and channel change in the study systems, and how they can be represented in an integrated flood model? (2) How do geomorphic processes, including landslides, debris flows and channel storage affect flood risk? (3) How will flood risk change in the future given expected changes in geomorphic processes? The integrated modeling framework will evaluate how processes interact over a range of temporal and spatial scales during and between flood events, shaping sediment dynamics, river conveyance, and flood frequency. Improved understanding of flood and landslide risks in these systems will provide valuable information for management decisions to address future flood risks and will be communicated via stakeholder workshops.