August 15th, 2016

U.S. Northern Gulf Floods

Posted at 1:43 PM ET

north-gulf-flood1-sm2In the U.S. Northern Gulf States, a significant and historic flood event has affected areas of southern Louisiana and Mississippi. Flood impacts have been particularly severe in areas of Baton Rouge and Hammond, Louisiana. Media reports indicate at least six fatalities, several thousand water rescues and at least 2,700 homes affected. It will take some time to fully assess the scope and severity of impacts of this event, and our thoughts are with those lost and directly affected by this event.

Meteorological/Hydrological Summary

A period of excessive rainfall has affected areas of the Northern Gulf, with most severe rainfall amounts over areas of Louisiana and Mississippi. This was enabled by a developing tropical disturbance that drifted slowly westward across the Northern Gulf states over the past week. The disturbance acted to produce widespread shower and thunderstorm activity in the presence of abundant moisture and unstable air. As the disturbance crossed Louisiana last Saturday, it produced periods of very intense rainfall for widespread areas, with unofficial rainfall rates exceeding two to four inches per hour.

north-gulf-flood1-lgGeneral outlook for significant river flooding. Source: National Weather Service

north-gulf-7-day-8-142-lgRadar-estimated seven-day rainfall. Ending 8 a.m. EDT August 14. Source: NOAA, U.S. National Weather Service

north-gulf-30-day-rain-8-143-lgThirty-day percent of normal rainfall (radar estimated). Ending 8 a.m. EDT August 14. Source: NOAA, U.S. National Weather Service

north-gulf-comite-river4-lgHydrograph - Comite River near Comite Joor Rd. Source: NOAA, AHPS, USGS

north-gulf-amite-river5-lgHydrograph - Amite River at Denham Springs. Source: NOAA, AHPS, USGS

Hazard data illustrated in the CAT-i map was taken from GC AdvantagePoint®, Guy Carpenter’s web-based risk management platform. GC AdvantagePoint users can view impacted areas on any map as well as see how their portfolios were affected. Please contact your broker or cat modeling analyst for further information.

Storm-total rainfall amounts have unofficially reached 31.39 inches near Watson, Louisiana, according to the U.S. Weather Prediction Center (WPC). Other notable rainfall totals include 21.60 inches at Lafayette Regional Airport and 19.14 inches at Baton Rouge Ryan Municipal Airport. Rainfall amounts of 22.84 inches have been reported near Gloster, Mississippi. Further east, storm-total rainfall amounts of 14.43 inches were reported by the WPC near Panama City Beach, Florida. Thirty-day rainfall amounts have exceeded 400 to 600 percent of normal for large areas of southern Louisiana and southwestern Mississippi, according to estimates of the U.S. National Weather Service (NWS).

The intense rainfall rates and excessive rainfall amounts have produced widespread flooding and flash-flooding, with most severe impacts over southern Louisiana. Record flooding has been observed on the Amite, Tickfaw and Comite Rivers. Areas of East Baton Rouge, Livingston, St. Helena and Tangipahoa Parishes have sustained severe flooding, to include areas of Baton Rouge and Hammond, Louisiana. Floodwaters have since started to recede.

The responsible area of low pressure has since merged with a surface front over Texas and followed the front into the Central Mississippi Valley, where heavy rainfall remains an ongoing concern. The frontal system is expected to cross into the Southern Great Lakes for Tuesday and then the Northeast for Wednesday to produce rainfall amounts of two to four inches, according to the WPC. Meanwhile, abundant tropical moisture should remain over Texas and the Lower Mississippi Valley to produce more showers and thunderstorms. Additional rainfall amounts of two to four inches are possible over already saturated soils to produce an ongoing threat of flash-flooding for these areas, according to the WPC.

The NWS maintains flood and flash-flood watches and warnings for areas under potential or imminent threat (weather.gov).

Selected Unofficial Rainfall Amounts (Storm Total)

Source: NOAA/WPC

Location Amount (inches)
LOUISIANA
NEAR WATSON 31.39
NEAR BROWNFIELDS 27.47
NEAR MONTICELLO 26.26
WHITE BAYOU/ZACHARY 26.14
LIVINGSTON 25.52
LAFAYETTE REGIONAL AIRPORT 21.60
BATON ROUGE/RYAN MUNICIPAL AIRPORT 19.14
NEAR LAKE CHARLES 18.10
MISSISSIPPI
NEAR GLOSTER 22.84
NEAR LIBERTY 10.97
WILKINSON 10.25
CENTREVILLE 10.20
FLORIDA
NEAR PANAMA CITY BEACH 14.43
HATCH BEND 14.00
NEAR BRONSON 12.80
NEAR VERO BEACH 12.16
CROSS CITY AIRPORT 11.39
TYNDALL AFB 11.03
NEAR MIRAMAR BEACH 10.17
NEAR SPRING HILL 10.06
MIDWAY 10.00
PENSACOLA NAS 9.95
ALABAMA
GLOSTER 9.94
NEAR FAIRHOPE 8.97
NEAR SILVERHILL 8.61

Impacts

Media reports indicate at least six fatalities as a result of this event. Emergency crews have rescued at least 20,000 people from swamped vehicles, flooded homes and threatened hospitals, according to reports. The Ochsner Medical Center in Baton Rouge, Louisiana has evacuated about 40 patients and may evacuate more. Over 10,000 have been reported staying in shelters.

A state of emergency has been declared for both Louisiana and Mississippi, according to media reports. A disaster declaration has been made by President Obama to enable federal aid for East Baton Rouge, Livingston, Saint Helena and Tangipahoa Parishes. At least 1,700 Louisiana National Guard members have been activated to support response efforts.

Emergency management officials indicate more than 1,000 homes flooded in both East Baton Rouge and Livingston Parishes. Reports also indicate at least 200 and 500 homes flooded in Saint Helena and Tangipahoa Parishes, respectively. These numbers may rise following post-event survey efforts. Nursing homes and hospitals are being monitored for possible flood impacts. Along Interstate 12 between Tangipahoa Parish and Baton Rouge, reports indicate that about 125 vehicles were stranded.

Media reports indicate that AT&T wireless equipment was damaged, causing service disruption for some customers. Amtrak has been using bus service for customers traveling between Jackson, Mississippi and New Orleans, Louisiana.

Sources: Agence France Presse, Associated Press, Reuters, U.S. National Weather Service, U.S. Weather Prediction Center, The Weather Channel.

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Guy Carpenter publishes CAT-i reports for major natural catastrophes worldwide. These reports cover catastrophes including worldwide tropical cyclones, earthquakes, major UK and European floods and any other natural event that is likely to incur a significant loss to the (re)insurance industry. Please email CAT.i@guycarp.com if you wish to be added to the free email distribution list.

Guy Carpenter compiles RISK-i reports for major technological or man-made events worldwide. These reports cover risks to property, transport and life including explosions, fires, crashes, engineering disasters and terrorist attacks that are likely to incur a significant loss to the (re)insurance industry. Please email RISK.i@guycarp.com if you wish to be added to the free email distribution list.

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