COM 0560.020 2002-2004 - Laserfiche WebLink

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LJniversi~ Terrace not been well mapped up to that point. The Waiakea watershed had been better studied; in the 1980s, a traditional steep-walled flood control chamiel was installed from Waiakea Pond, near the coast, to the area near the University of Hawaii at HIlo. As residential subdivisions marched up the 35-square-mile watershed drained by the Waiakea Stream, the natural watercourse was walled and channelized where it passed through and along housing developments. URS Corporation, which was hired by the county to redraw flood maps - and recalculate 100-year flows -for the Waiakea and Palai watersheds has reset the clock, so to speak, on 100-year floods. The bar has been raised, and now the November 2000 flood record has come to define the new 100-year peak flood. More precisely, the flooding experienced that month was something less than what Hilo can expect to experience once every 100 years. According to Ray Lenaburg of the Federal Emergency Management Agency, "we have come up with a new 100-year [flood] dischazge, and that's what we're using in the new maps." "The old peak discharges have been superceded based on a new analysis," Lenaburg told Environment Hawai ~i in a telephone interview. The new figures, he said, came about after a consultant reviewed data from two gauges in the area and ran them through the standard log-Pearson 3 method of determining distribution. "We thought it was aone-in-100-yeaz flood," Lenaburg said of the November 2000 event, "but when we went back and looked at the data, it was less than aone-in-100 yeaz flood." To protect built-up azeas from future floods, the county and the Corps of Engineers have begun to work on a multi-year project that will lead eventually to construction of amile-and-a-half-long channel and another 1,100-foot-long levee along an existing channel. The new channels would cause the flow in Waiakea Stream to be divided into two watercourses above the Kupulau Bridge, site of some of the heaviest flooding in 2000. The two branches would rejoin at the start of the channelized Waiakea Stream, near the bridge at Komohana Street. The project, if it works out, won't provide relief for homeowners for a while yet. At a December meeting with concerned members of the public, county engineer Dennis Lee outlined the Corps' best-case timeline. From January 2003 to January 2005, the feasibility study will occur. Another year -July 2005 to July 2006 -will be required to draw up plans and specifications. Barring unforeseen delays, construction might be completed by July 2008. The estimated cost is on the order of $17 million. Besides the new work on the Waiakea Stream, the Corps of Engineers will be repairing flood channels on Alenaio Stream and the lower reaches of Waiakea Stream, channelized in 1985. Total cost of repairs is put at about $4.2 million. Double Whammy