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<br />1.4 <br /> <br />1.4 Orqanization of Report <br />This report is organized into six chapters. Chapter I contains a statement <br />of the purpose and scope of the investigation, Additionally, as background to <br />the study methodologies, a general overview of the characteristics of hypercon- <br />centrated sediment flows is presented. Chapter II pl'esent.s a qual itative <br />assessment of the physic~ attributes of the study area which infiuence the <br />flood-hazard conditions within the town of Telluride. Chapter III provides an <br />assessment of the geology and soils present in the Cornet Creek basin and their <br />affect on the occurrence of mud flows. Chapter IV discusses the hydrologic <br />conditions affecting Cornet Creek, reviews past hydrologic studies of the stream <br />and presents an analysis for the estimation of mud flow hydrographs of specific <br />return period. Chapter V reviews the development of the 2-D hyperconcentrated <br />sediment flow-routing model MUDFLOW. Chaptelr VI documents the hydraul ic analysi s <br />conducted on Cornet Creek to delineate flood-hazard areas within the town of <br />Telluride. Flood-hazard maps discussed in Chapter VI are presented in Appendix <br />A as a separate volume. Chapter VII represents the summary and conclusions for <br />the study. <br /> <br />1.5 Description of Mud Flows <br />This section is provided to familiarize the reader V1ith the general <br />properties and behavior of viscous, hyperconcentrated sediment flows. <br />Hyperconcentrated sediment flows encompass a range of sediment concentrations <br />from 20 to 50 percent by volume and include the categories of mud flood and mud <br />fiow. A general classification for flows as a function of sediment concentration <br />is presented in Table 1.1. The classification system and fluid properties for <br />such flows presented in the table are based on termi no logy defi ned by the <br />National Research Council (NRC, 1982) and research conducted at Colorado State <br />University (O'Brien, 1986). <br />Mass wasting processes are separated into several categories according to <br />fi ow pro pert i es by the Nat i ona 1 Research Counei 1 Commi ttee on Methodo log i es for <br />Predicting Mud Flow Areas (NRC, 1982). The four categories include landslides, <br />mud flows, mud floods,and clear-water floods. Conventional water flooding and <br />mud fioods are classified under the Nationa-I Flood Insurance Program (NFIP) <br />definition of fioods by the NRC. Both flood types display inherent fiuid <br />properties and are referred to as hydraulk flo~ls. Mud floods were defined by <br />the NRC as transporting high sediment concentrations (as much as 50 percent by <br />