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This project focused on the probable effects of three different magnitude lahars on the ground and surface water in the areas of King and Pierce Counties surrounding Mount Rainier. The data used for this project was acquired from King and Pierce Counties, the State of Washington, and the United States government. The goal was to use existing data that was available at little or no cost to promote the use of this model in other research projects or disaster mitigation planning. The vital piece of information, the three different magnitude lahar extents, was provided free of charge by the USGS as an output of LAHARZ; their mathematically advanced lahar inundation flow model. The three flow magnitudes, originally classified by the USGS as Case I, Case II, and Case III, were reclassified for this project as Extreme, Severe, and Moderate, to better illustrate the effect on the surrounding resources.
The primary concerns were possible impacts to critical aquifer recharge areas and salmon and aquatic organism habitat. The affected percentage of the total population in King and Pierce Counties based on the lahars ranged from 19.95% in Extreme flows, 16.61% in Severe flows, to less than 0.01% in Moderate flows. The percentage of critical aquifer recharge areas in the two counties affected by the Extreme lahar was 24.78%, Severe flows had 15.79% affected, while Moderate flows had 1.92% potentially contaminated. The salmon habitat in two counties was greatly affected by the Extreme flow event with 41.73% of habitat affected. The Severe flow event still had a significant effect on the habitat with 25.09% affected. The Moderate flow event had a relatively small impact of 0.78%. The aquatic organism habitat was also greatly affected by the Extreme lahar with 72.32% potentially contaminated. The effect on aquatic habitat in the Severe lahar dropped greatly to 27.13%. The Moderate lahar affected 8.94% of the aquatic organism habitat. The model has the potential to be expanded and improved upon with the use of additional data, such as municipal water supply locations, that was not available for this research due to security concerns or costs associated with the acquisition.