EAS 205 October 16th In class lecture notes (Streams and Flooding) Correspond with Lecture Notes provided by Prof

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Earth and Atmospheric Sciences
Solweig Balzer

October 16 , 2013 (Streams and Flooding Notes) Flood Hazard Mapping  For future modifications of area  Used for later on when it floods, what kind of resources do I need to help out  Will relocate things, but not everyone  Just map the area Zoning  Keep important structures out of areas prone to flooding o Can only build these kinds of structures here o Don’t build on a one year floodplain … maybe a 25 year floodplain is okay for some structures o Can increase areas by adding fill, build it up to allow extra space to accommodate housing… building it up higher not wider, its LESS likely that you will have flooding… reducing the risk… if you do have a flood, it will be minor flooding Flood proofing  Build on stilts  Above the high water mark  A lot of places that have troubles with tsunami’s will tend to build on the second floor… the bottom floor is the parking lot.. tend to build from second floor up (Hawaii)  Enclosed bottom of house.. go up stairs to get in… store material down there that they don’t mind getting those things wet. Designer homes?  Designs for floodplains Retention ponds  Hold off extra water, not usually from flooding. Its to hold back water from entering river systems  Depressions (sediment bases)… put in a number of different locations … (lake summerside, fountain lake) purpose is too hold back water. Try and promote drainage elsewhere  On the side of the slope, dam like area, the water will take its time to get to the river and at that point it wont flood anymore or it will jus evaporate up.  Natural wet areas for waters to pond… if you don’t put a hole there again, you’re going get a lot of flooded basements Diversion channels  Artificial channels  Many connected to the Mississippi  Purpose: to push extra water that the river cant carry because flood risk or about to flood.. to an area that you don’t want to flood -> this area wasn’t supposed to get that water.  Diverting it, but problem: someone else is getting more water than they should be getting and they flood worse and often more frequently because that river in that area isn’t big enough to accommodate for the amount of water being sent that way The down side?  1997, lot of water, need to drain someplace.  Divert the waterway from an expensive area… limit cost damages (saving lives is secondary, or even lower) its more expensive to flood Winnepeg than it is to flood farmland… given the choice you want to flood farmland.  Moral issue, lots of people living there? Old river control structure  1973 low sill structure almost a disaster b/c they forgot about the sediment. They were only monitoring water  decided this would be a good navigational shortcut to another river…unfortunately when they cleared off the degree, the Atchafalaya is faster … so when they opened it… the Mississippi wanted to migrate to the Atchafalaya (& still does)  would have lost the Mississippi -> if the sills had failed completely.  If Atchafalaya doesn’t get enough sediment then it will erode Problems?  Have to transfer the water  Still migrating it over  Really expensive  It keeps getting flooded (Mississippi)  Water levels have been
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