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<br />2.3 Principal Flood Problems <br /> <br />The main cause of flooding in Pierce is usually intense rainfall in <br />the late spring and thunderstorms in the summer, which are often <br />accompanied by hail. <br /> <br />Documentation of historical floods and damage estimates in Pierce is <br />sparse. Based on interviews with the Mayor, it was determined that <br />Pierce has experienced several flood events dating back to the <br />1920s. The Mayor recalled major flooding in 1935, 1951, 1954, 1961, <br />1965, 1972, 1974, and 1977. The more severe floods occurred in <br />1935, 1965, and 1972, when floodwaters overtopped Rowe Avenue and <br />u.s. Highway 85, then continued on to flood areas west of 1st Street <br />to areas as far as 0.5 mile east of the highway. Past floods have <br />caused erosion of town streets, flooding of basements, damage to the <br />pierce water system, and clogging of the Pierce Lateral Canal from <br />sediment produced by upper basin runoff (Reference -3). <br /> <br />These typical flood damages were also observed by personnel of the <br />study contractor the day after the flood of May 1, 1977, when approxi- <br />mately 2.62 inches of rain fell on Pierce during a 40-minute thunder- <br />storm. The extent of the flood plain at numerous locations was <br />plotted on an aerial photograph of the Town of Pierce and verified <br />by interviews with the townspeople. The floodwaters had washed out <br />several sections of the Pierce Lateral Canal, eroded the road approaches <br />to the Rowe Avenue bridge, eroded nearly all of the streets on the <br />east side of town, flooded numerous basements, and deposited thick <br />layers of silt over large areas in the east side of town. <br /> <br />The Town of Pierce has several drainage problems, including the lack <br />of storm sewers, buildings which have been constructed with first- <br />floor elevations below town roads and intersections, and flooding <br />from Spring Creek. Flooding on the western side of the Union Pacific <br />Railroad tracks has resulted from the inadequate capacity of the box <br />culvert for Spring Creek under u.S. Highway 85 and from overflow of <br />the pierce Lateral Canal. Flooding on the east side of town is due <br />to overflow from Spring Creek and excess floodwaters from the west <br />side that flow over the Union Pacific Railroad tracks. <br /> <br />2.4 Flood Protection Measures <br /> <br />No flood protection structures either exist or are proposed which <br />would reduce the flood hazards in the Town of Pierce. <br /> <br />4 <br />