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2.5 Conservation Board and the town was conductl~d on September 11 and 12, 1986. After execution of the project contract with FEMA, a second deta i 1 ed fi e 1 d reconnaissance was conducted by SLA personnel on October 5 through 9, 1987. The detailed field reconnaissance included a cross-sectiona-I survey of the Cornet Creek channel through the town, measurement of all hydraulic structures along the stream and inspection of watershed areas. Several other tri ps to Tell uri de by SLA project personnel were also used to further observe potential sediment sources and the hydrologic character of watershed areas. 2.2.2 Watershed Observations The Cornet Creek channel has incised through glacial and postglacial deposits in the lower portion of the watershed, This material is believed to be the major sediment source contributing to mud flow events. During the field reconna i ssance, two slope fail ures were i dent i fi ed in the area that supply sediment, boulders and debris to the channel. Both of the slope failures are downstream of a 40-foot high waterfall located along the main Cornet Creek channel. The mud and debris deposits at the mouth of Cornet Creek contain substantial quantities of fine sediments such as clays, silts, and fine sand. Significant fine sediment are not supplied from the upper watershed, The upper Cornet Creek watershed does, however, provido significant runoff area. The steep slopes, large areas of rock outcrop and lack of soils in the upper basin promote rapid surface runoff. Significant runoff from the upper watershed will entrain and transport material from lower areas of the basin through channel and bank erosion. Unstable slopes abutting the creek in the lower watershed provide a large source of transportable sediment resulting in mud flows, as historically observed. 2.2.3 Channel Observations Upstream of the canyon mouth to the location of the falls, the channel was observed to be mildly obstructed by boulders and debris. The potE~ntial exists for large volumes of sediment to be supplied to the channel during a significant flood from several bank erosion areas in the lower watershed. In the central port i on of the watershed, the channel is confi ned by steep valley slopes and dense vegetation. High flows along the channel in this area would be inhibited by the dense trees and vegetation growing adjacent to the channel.