State Water Resources Research Institute Program (WRRI)

Details for Project ID 2002LA1B, 2002

Flooding in a New Orleans Watershed Caused by Hurricanes That Do Not Overtop the Levee System

Institute: Louisiana
Start Date: 2002-03-01 End Date: 2003-02-28
Total Federal Funds: $17,000 Total Non-Federal Funds: $34,546

Principal Investigators: Donald Barbe, John McCorquodale, Gianna Cothren

Abstract: New Orleans is a unique metropolitan area for many reasons, one of which is its storm water drainage system. Most metropolitan areas around the world use gravity flow for discharge of urban drainage. New Orleans is at or below sea level and therefore must lift (pump) the areas urban runoff produced from its average annual rainfall of 58 inches. Because of this, hurricanes and the associated flooding are of great concern to water resources planners. This research examines hurricanes based on the flooding that would be caused by the combination of hurricane-associated rainfall and diminished pumping capacity due to storm tides. Hurricanes that do not overtop the levee system but still diminish the pumping capacity because of increased tides will be used. The study area is the watershed in New Orleans drained by Drainage Pump Station No. 4 (DPS #4). DPS #4 drains some 4,800 acres by discharging the storm water runoff into Lake Pontchartrain. This watershed has been impacted by 14 hurricanes that have caused significant damage and by 28 other hurricanes and tropical storms that have caused minor damage. The discharge head(s) for the analysis of DPS #4 are based upon hurricane storm surge data from the National Weather Services Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model. The predicted storm surge are used as the outlet elevation for DPS #4 to estimate the capacity of the station for the different categories of storms. Hurricane Danny, a slow category 1 storm, and Hurricane Fran, a fast category 3 storm, are used. Rainfall intensities are then synthesized to compare the potential of different hurricanes that would result in flooding of the watershed. The flooding of the watershed is estimated by use of the U.S. EPA Storm Water Management Model (SWMM). The flooding obtained is in terms of volume of excess storage capacity. The above research has been completed. The objective of this proposed research is to convert the volume of excess storage obtained above into depth of flooding in the watershed, and finally into dollar cost of the flooding.