Laserfiche WebLink
<br />entrance angle and existence of an entrenched channel at the <br />apex determine the initial flow pattern on the fan. <br />Pronounced geomorphic bias (topographic variation which <br />confines the flow area to a part of the fan) forces the flow <br />into a confined path and reduces the instability of :he flow <br />direction. Avulsions are less common on a fan which is <br />bi~sed or entrenched. resulting in more stable flood <br />patterns. <br /> <br />The correlations between these characteristics and all <br />hazards except unpredictable flow paths are dependent on the <br />position of the stable flow path. If a structure is within <br />the established path, the likelihood of damage is very high. <br />Conversely. if the structure is outside of the established <br />path. it is unlikely that it will be damaged at all. An <br />entrenched or topographically confined channel will also <br />convey large volumes of sediment and water to the lower <br />portions cf the fan. causing high ha=ards down-fan. <br /> <br />~ Veqetation <br /> <br />If a fan is well vegetated. erosion processes are <br />considerably slower than on a poorly vegetated fan. The <br />amount of sediment being transported down-fan is less, while <br />the increased roughness results in lower velocities. flow <br />paths and channels are much more stable. since bank erosion <br />processes are slowed and deposition of sediment in the flow <br />path is reduced. Consequently, a well-vegetated fan will <br />experience substantially smaller hazards than a poorly <br />vegetated fan. <br /> <br />Location. Densitv and Geometrv ~ Develocments <br /> <br />A developed area such as a subdivision greatly alters the <br />local geometry and dynamics of the flow. Concentration of <br />flow between structures, ponding of water and sediment <br /> <br />51 <br />