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FLOOD HISTORY <br /> Flooding problems have been largely due to localized high <br /> intensity rainfall from about 1,000 feet elevation to 5,000 feet <br /> elevation. Such storms can occur anywhere along the mountain slopes <br /> of South Kona. In addition to these localized storms, a few general <br /> storms have occurred covering the whole width of the study area. <br /> According to storm damage reports by SCS, there have been 17 da- <br /> maging floods since 1956. Other floods have occurred before this <br /> date but no detailed accounts are available. <br /> Most of the flood damages were due to poorly defined <br /> watercourses, the presence of developments in these watercourses, and <br /> the absence of properly constructed road crossings. During large <br /> storms, floodwaters overflow onto and erode adjacent lands. Further <br /> downstream, sediment and debris accumulate and compound the problem <br /> in roads and in homes that have been built on some of these poorly <br /> defined watercourses. <br /> Accurate data on rainfall and flood flows are nonexistent but <br /> general accounts are available from storm damage reports. <br /> Recent Notable Floods <br /> March 31, 1956 <br /> Rainfall was estimated at about 8 to 12 inches with the highest <br /> intensity occurring from 6 to 9 p.m. This rainfall amount was <br /> greater than the 100-year, 24-hour frequency storm event as defined <br /> in the U.S. Weather Bureau Technical Paper No. 43. Damage occurred <br /> throughout the South Kona area along the Mamalahoa Highway. Examples <br /> of damages are flooding of the Honaunau Post Office building and <br /> several segments of Mamalahoa Highway. <br /> April 29, 1963 <br /> Approximately 4 inches of rainfall fell within 2 hours. Total <br /> rainfall amount was equivalent to the 100-year, 24-hour frequency <br /> storm. Damages resulted in losses of 0.25 to 1.5 inches of soil from <br /> bare truck crop lands. Several macadamia nut and coffee orchards <br /> ware severely eroded and trees were lost. Damage occurred to Hookena <br /> Road. <br /> The watercourse crossing the Mamalahoa Highway near the <br /> Greenweli property (see Fig. 1) resulted in considerable erosion <br /> damage below the road. <br /> Many of the watercourses experienced flows but little damage <br /> resulted. The town of Kainaliu, near the study area, was flooded. <br /> <br /> t -5- <br /> <br />