Storm surge levels exceed six feet along the Mississippi Coast and Lake Pontchartain shoreline tonight, according to NOAA Tides and Currents gauges. Persistent south winds are keeping storm surge pushed into the Mississippi Sound, which both floods the Mississippi Coast and hinders the outflow of high water in Lake Pontchartain. Meanwhile. surge levels in Shell Beach, LA, have fallen below five feet, as water is being pushed away from this community and into Lake Borgne.
High water has been reported in several communities that drain into the Gulf or Lake Pontchartrain Basin. WAFB interviewed people in the Lake Pontchartain watershed who were flooded for the first time. These people said they were not flooded from any other tropical systems, including Hurricane Katrina. Apparently, heavy rain water is not draining as quickly as normal, due to elevated water levels in Lake Pontchartain, the LA and MS coastal region.
This phenomenon is consistent with observations from Tropical Storm Debbie in Florida this past June, which flooded many communities as rainwater drained slowly due to elevated water levels in Tampa Bay. Also, SCIPP conducted 62 weather/ climate needs assessment surveys this past year, finding that several stakeholders in the Houston/ Galveston area reported slow rainwater drainage when water levels are elevated due to elevated surge levels in Galveston Bay.
Such impacts are localized, but are important for those affected. It's also important to realize that some of these flood patterns are representative of a large, slow-moving hurricane or tropical storm, which dumps large amounts of rain. Although the history books may not remember Isaac as destructive as Katrina, for some people the impacts of Isaac were worse.
Such lessons may also help us to look separately at the severe weather impacts of future hurricanes. Hurricanes generally throw a three-pronged threat at us, as we are threatened by strong winds, heavy rain and storm surge. It is helpful to think through the potential impacts for each of those hazards with any given storm, which may change drastically, depending on the size, forward speed and duration of the storm.
