Puyallup Flood Alert Completed

WA388 - Floodwater Monitoring and Simulation on the Puyallup River and Real-Time Flood Alert and Flood Simulation of River Discharges in the Puyallup River Basin - Completed 2001

Problem - The Puyallup River basin lies mostly within Pierce County, Washington, and contains 972 square miles of land ranging in elevation from zero at its mouth in Puget Sound to 14,408 feet at the top of Mount Rainier. Accurate estimations of flood peak timing, peak stage, peak volumes, and duration of flood flows at various points on the major channels within the Puyallup stream-channel network are necessary to aid planning activities during high-water periods. The Pierce County River Improvement Agency is responsible for floodplain management on the Puyallup River system and is primarily responsible for maintenance of flood control structures and mitigation of flood hazards. In order to make their operations more efficient and effective, they desire a functional alert system that will provide information about impending flooding. The agency is also concerned with how various streamflow regulation measures and floodplain activities may affect flooding in the river. Without a more complete understanding of the basin hydrology and channel hydraulics of the watershed, it is difficult to assess the magnitude of the impact of these stream modifications on flooding.

Objectives - The objectives of this project are to enhance the present flood warning system, provide a tool to the agency to assess current hydrologic conditions of the watershed and make short-term simulations of possible flooding, and apply a channel-routing method to accurately route floodwaters through the major river channels in order to account for various regulations and diversions that may be imposed on the system.

Relevance and Benefits - This project provides Pierce County with the technology and a calibrated watershed model to make their own hydrologic forecasts. The forecasts will be used to efficiently deploy their resources to critical areas during floods, and possibly save lives and property. Specific benefits to the USGS that are provided by this project are opportunities to 1) calibrate a watershed model for use as an operational forecast model; 2) create a user-interface to facilitate the user to make data retrievals, to make data conversions, to make model runs, and to visualize simulation results; 3) demonstrate to the public that the USGS can be successful in developing a fully integrated real-time operational system of a data-collection network feeding a hydrologic model and displaying the simulated results as meaningful graphics and text files; and 4) demonstrate the integration of National Weather Service forecast data with an operational hydrologic model.

Approach - The existing real-time telemetry network of streamflow and meteorological gaging stations will be enhanced with newer computer display capabilities and an increased gaging network. The computer-display enhancement will provide a visual display on a computer in the agency's office of those stream and precipitation gages in the Puyallup Basin that have exceeded threshhold. An operational computer system will be applied to the basin to collect and manage all of the streamflow and meteorological data available on a real-time basis. A numerical model of the Puyallup watershed will be integrated into the operational system to simulate the complex hydrologic and hydraulic processes occurring in the basin. The system will have the capability to maintain continuity of the simulation processes in real time so that the flooding potential of the basin can be monitored periodically as data become available. The system will also provide comparisons of simulated streamflows and observed streamflows and allow the user to adjust the simulations with a minimum of effort until a reasonable comparison is obtained.