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Flood Hazards

Image of flooded land

Flooding is the natural hazard of most concern in Washington and affect lives in the State every winter and spring. Flood monitoring, forecasting, and warning methods allow for planning of responses to potential floods, but flood-inundation maps needed by local planning agencies to assess flooding and floodplain issues are seriously outdated. Flood frequency and magnitude are the basis for many planning decisions, but limited databases and changing conditions make determination of 100-year floods and other frequency discharges an uncertain science. The effects of land alterations on the frequency and magnitude of floods is unclear. Urbanization creates large and small streamflow and ground-water flooding issues that seldom occurred in pre-development times, such as snow- and ice-clogged storm drains or flooding in low-lying areas because of rising ground-water levels. Effects of forest practices on runoff and flooding are contradictory and unclear. Dams alter the hydrology of a watershed, reduce channel capacities through sediment aggradation, and present unknown flood-related issues if removed. Increased technical information is needed on these flood-related issues.

USGS gages on streams in Washington have provided information on flood monitoring since about 1900, and the present network of stations, computer links, and real-time data operated by the USGS remains one of the foremost networks in the country. The network provides real-time streamflow data from 160 gaging stations via radio, satellite, computer, and dedicated phone lines to local public utilities districts and power companies. Availability of real-time streamflow data on the Web now allows not only public agencies but the public themselves to make use of the information at critical times.

As part of the USGS Natural Hazards Project in the Seattle area, the Water Science Center developed a method for using real-time streamflow data, Geographic Information System mapping capabilities, and a computer delivery system to provide real-time maps of projected flood inundation and depth during storms. This Project also produced regional flood-frequency analyses, estimates of hazards caused by channel migration, and maps of areas prone to ground-water flooding. The USGS also conducts numerous flood-frequency and flood-simulation studies and updates flood-frequency analyses for the State. USGS scientists developed a flood-simulation model and a flood forecast system for the Puyallup River Basin and assessed flooding potential in the South Prairie Creek Basin. Some USGS projects include studies of key processes in major floods, such as rain on snow. Discharge measurements at more than 200 gaging stations throughout the State provide information on channel changes over the years.

Current and Recent Regional Hazards Studies Conducted by the Washington Water Science Center
Cedar River Peak Flow Management
Geomorphic and hydrologic study of peak-flow management on the Cedar River
Geomorphic Mapping, Dosewallips River
High Resolution Geomorphic Mapping of the Dosewallips River Using Remotely Sensed Data: Method Development - Completed FY2004
FEMA Technical Support
FEMA Technical Support, Pre-Declaration, January 2009 Floods - Completed FY2009
Green River Geomorphic Responses
Geomorphic Responses of the Middle Green River to Floods - Completed FY2008
Howard A. Hanson Reservoir
Estimating Runoff-Season Inflows to the Howard A. Hanson Reservoir, Green River - Completed FY2002
Honduras Flood Mapping
Flood-Hazard Mapping in Honduras by the USGS Washington Water Science Center - Completed FY2002
Evapotranspiration at Klamath Marsh and Lower Klamath National Wildlife Refuge
Estimating Evapotranspiration at Klamath Marsh, Oregon, and Lower Klamath National Wildlife Refuge, California - Completed FY1999
Puget Hazards
Urban Hydrologic and Geologic Hazards in the Puget Sound Area - Completed FY2003
Mount Rainier Fluvial Geomorphology and River Sedimentation
Geomorphic Analysis of the Fluvial Response from Sedimentation Downstream from Mount Rainier, Washington

Flood-Carrying Capacity and Sedimentation Trends of the Lower Puyallup River System - Completed FY2010
Multispectral imaging, Puyallup River
The Integration of Multispectral Imaging and LIDAR to Evaluate the Geomorphic Changes Associated with a Levee Setback Along the Puyallup River, WA - Completed FY2005
Puyallup Flood Alert
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 FY2001
South Prairie Creek
Flood Potential of South Prairie Creek - Completed FY1999
FEMA High Water Marks - Western Washington Flood, January 2009
Assessment of Flooding in Western Washington, January 2009 - Completed FY 2010
Flood Frequencies
Flood Frequencies in Washington - Completed FY1999

Magnitude and Frequency of Floods In Washington - Completed FY1974
Ground-Water Records
Collection of Basic Ground-Water Records, Washington
Hydrologic Urban Indicator
Hydrologic Indicators of Urban Development in Western Washington Streams - Completed FY2002
Precipitation Records
Collection of Basic Precipitation Records, Washington
Rain-on-Snow Events
Magnitude and Frequency of Water Available for Runoff During Rain-on-Snow Events at Selected Sites in Washington State - Completed FY1996
Surface-Water Records
Collection of Basic Surface-Water Records, Washington

Real-Time Hydrologic Data by Independent GOES Telemetry System in Washington - Completed FY1991

Compilation of Miscellaneous Streamflow Measurements in Washington - Completed FY1989

Streamflow Statistics and Drainage Basin Characteristics for the Southwestern and Eastern Regions, Washington - Completed FY1985

Low-Flow Analysis of Selected Streams In Washington - Completed FY1985

Streamflow Estimates for Small Streams in Washington - Completed FY1982

Flood Profiles - Completed FY1981

Re-evaluation of the surface-water gaging station network - Completed FY1978
Yakima Watershed and River Systems Management Program
Yakima Watershed and River System Management Program (WARSMP) - Completed FY2002

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Page Last Modified: Tuesday, 18-Jun-2013 11:20:32 EDT