Laserfiche WebLink
<br />'15 <br /> <br />--- <br /> <br />--- <br /> <br />The major concern in relationship to floodproofing is adequate erosion protection of chan- <br />nel banks, earth fills, berms and levees, Where flood waters impinge upon or flow along <br />earth structures, significant erosion can occur. Figures 3,1 and 3.2 show a sequence of bank <br />erosion occurring during a flood and resulting in erosion of the bank and lateral movement of <br />the stream to where the ground was eroded from under the house. Severe erosion, called <br />local scour, can occur where flood waters impinge against piers or piles and around the <br />edges of walls, These areas must be protected with adequate measures such as riprap to pre- <br />vent erosion and failure of the structure, <br /> <br />3.6 Debris <br /> <br />Debris refers to floating material that is picked up and transported downstream by the flood <br />waters. In a natural flood plain, debris consists mainly of brush and trees that fall into the <br />channel. This occurs as flood waters erode and undercut channel banks, Eventually, the bank <br />starts to slough and any vegetation or trees at the bank fall into the channel. With human <br />development in the flood plain, debris can range from rags and fences to cars and parts of <br />structures. <br /> <br />Like sediment, debris can cause blockage of the channel resulting in increased flow depths <br />and diversion of flow from the original channel. The main concern is for the impact forces <br />that occur when floating debris collides with a structure in the flood plain, Impact loads must <br />also be considered when the structural design is being done. <br />