How Rare Was the August 2016 South-Central Louisiana Heavy Rainfall Event?

Abstract

This study examines the spatiotemporal characteristics of the historic 10–14 August 2016 south-central Louisiana precipitation event. The storm was the result of a moisture-rich, tropical low pressure system, also known as a tropical easterly wave, that slowly tracked westward along the Gulf Coast from Florida to Texas. Once over south-central Louisiana, the storm was able to take advantage of anomalously high precipitable water, broad low-level instability, and continuous moisture inflow from the Gulf of Mexico to produce historic rainfall. Totals exceeded 254 mm (10 in.) for much of southern Louisiana, while locations adjacent to Baton Rouge and Lafayette received upward of 635 mm (25 in.). One station measured a 48-h rainfall total of 797.3 mm (31.39 in.)—the greatest 48-h total on record for Louisiana. Using calibrated radar data, the Storm Precipitation Analysis System (SPAS) revealed that one location likely received >864 mm (34 in.) of precipitation during the duration of the storm, well over the estimated 1000-yr return interval. A synoptic discussion of the event and analysis of the storm’s recurrence interval helps place this storm in a historical context.

Modeling Temporal Accessibility of an Urban Road Network during an Extreme Pluvial Flood Event

“…The results show that the 500-year 24-h duration event applied uniformly over Lafayette Parish approximated the August 2016 flood event in terms of the available HWM data (NSE ¼ 0.96). This result corroborates the regional frequency classification arrived at by Brown et al (2020). The 500-year RMSE of 0.37 m obtained in comparison with the HWM data from the 2016 event is consistent with the 0.28-0.32-m performance range presented by Neal et al (2009) for whole city urban-flood simulations.…”

“…The flood of 2016 was taken as a representative surrogate for the 500-year regional event based on the work by Brown et al (2020), which provided a comprehensive assessment of intensity and duration of the event. The simulations suggest that much of the flooding in Lafayette Parish is pluvial, with peak 500-year depths ranging from 0.15 to 0.6 m with an approximate mean value of 0.3 m. Except for the Vermilion River, which is not the main source of residential flood risk, the entire parish was ungauged during the 2016 flood.…”

Assessment of inland flood hazard sensitivity to hydrological intensification in coastal watersheds

“…Although this region is protected from the annual flood pulse of the Lower Mississippi/Atchafalaya River(s), shallow riverine flooding occurs frequently in this region due to the poorly drained soils and flat topography. Notably, a devastating flood affected the Vermilion Basin in August 2016 whose ±500 mm, 2-day rainfall approximated the 500-year (0.2% annual exceedance probability) project design flood (Brown et al, 2020). Other notable floods have occurred in the region including the floods of 1927, 1940, and 2001(FEMA, 2018.…”