AG 1997 08 12 - Laserfiche WebLink

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Memorandum Page 3 August 6, 1997 Physical Actions There are a number of infrastructure type physical actions available. Some would require extensive cooperation, coordination with or even be the responsibilities of other levels of government. Creek cleaning is a visible act that removes stumps, fallen trees and debris from stream areas. The results of such an effort vary by how extensive an action is taken and whether areas up and down stream along with areas adjacent to stream areas are kept clean. Remember without natural cover, stream banks become exposed to erosion; and more importantly, there is little to slow rising waters down. Accelerated stream flows create greater erosion problems and pose severe safety issues. Creation of specific basin areas for stream overflow, detention and retention of high waters. This requires the development of an extensive system of reserved land areas for sto,m water retention and detention. Design of a system of this nature would require detailed engineering analysis and most importantly a standardized design criteria based upon some level of rain accumulated over a specified period (i.e., 6 inches over 24 hours). It would need to be understood that any system would fail if weather conditions exceeded design standards. Renovation and modification of existing drainage structures and areas where a damming impact is created during heavy rains. Most of the County's road drainage crossings were constructed many years ago. The Department of Transportation is responsible for maintenance and replacement of these facilities. When undersized culverts or older bridges restrict water flow, the results usually create ponding in upstream areas and erosion problems at the culvert or bridge area. Floating debris carried by rising water blocks these structures. During the July 23-24 storm, several bridges and roads were under water or washed out (see "Attachment B"). Reconstruction of these facilities including raising roadway approaches and/or adding additional overflow relief routes could help ease specific area flooding problems. Each of these approaches requires extensive study, engineering analysis and funding solutions. Summary There are certainly additional approaches that could be pursued regarding this issue. However, the impacts of each approach along with the cost-benefit analysis required to include how these efforts are to be funded are not simple to resolve. Finally, regardless of the direction the Board of