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cheat sheet - Rivers & Flooding- Unique features of...

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Rivers & Flooding - Unique features of rivers and floodplains- fertile soils, abundant water supply, proximity to shipping, ease of waste disposal; Delaware River Flooding April 2005 -Caused by major snow cover in Pocono’s and heavy spring rain (NW New Jersey & NE Pennsylvania), Rainfall caused by interaction between moisture from remnants of Hurricane Ivan, Worst flooding in 50 years along Delaware River, Consistent with 80 to >100-year floods, Lack of flood control plan; Stages of floods- 500 years (fill channel), 100 years (fill terrace 1), 2-3 years (fill terrace 2); In U.S. floods account for ~70% of presidential declared disasters each year; 9.6 million households and $390 billion in property lie in flood prone areas around the U.S.; Hydrologic Cycle precipitation evaporation infiltration runoff; Runoff - precipitation or snowmelt resulting in stream flow; 1972 Inland Floods - Hurricane Agnes produced floods over the North East, 122 deaths and $.4 billion in property damage; 1993 Great Midwest Flood- Junction of Mississippi, Missouri, and Illinois Rivers; Floodplain - Flat surface adjacent to river channel, periodically inundated by floodwater, make man made levees in order to occupy land; Drainage Basin - Area drained by a single river or river system; Natural levee - after many floods natural levees built up (max 6 meters); Flooding is a function of: Total amount of distribution and precipitation, Rate of infiltration and runoff, Topography; Discharge (Q)= W x D x V, Volume of water flowing past a point in a river in a specific amount of time, D= stage , Hydrograph represents discharge versus time; Flood forecasting - Examine past events (maximum annual discharge), Determine recurrence intervals of historical events by ranking, Extrapolating to future possibilities; Recurrence Intervals - average time between floods of a given size to determine need long-term record of annual peak discharge, (n+1)/m; Prevention- artificial levees- earthen mounds along banks which constrain river, flood walls - same as levees but concrete, reservoirs/ retention basins- holds water temporarily until flood is over; g- Increases flooding by making ground impervious (flash flood), Reduces lag time (amount of time between when rainfall occurs and the flood is produced) , Rate of urban growth in floodplains is approx 2x that of the rest of the country; Flooding in NJ - particular concern in this area b/c development has forced water to run off into streams and runoff that enters the Raritan has potential to cause harm to communities downstream (Bound Brook), Hurricane Floyd in 1999 causing damages to over 70,000 homes surrounding the Raritan, As of 2006 the township of Green brook has built 2 levees; Persistent problems: Communities that are heavily developed or built on flood plains are going to have consistent problems with flooding ; Floodplain Management - Prevention, adjustment, government buyout and relocating people from floodplain
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cheat sheet - Rivers & Flooding- Unique features of...

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