Littoral Drift and Erosion at Belle Pass, Louisiana

Channel enlargement and modifications to the jetties at Belle Pass, the mouth of Bayou Lafourche on the Gulf coast of Louisiana, had become necessary due to increased marine traffic by offshore oil and mining production and the fishing industry, along with the proposed development of nearby Port Fourchon. Permission for construction, required by the Corps of Engineers, was granted after map and aerial photo studies, field observations, and hydraulic model experiments showed that beach erosion, and especially littoral bypassing, would be insignificantly affected by extension to the existing single jetty and construction of a new twin jetty. The average annual recession rate of the coastline in the Belle Pass area between 1885 and 1932 was 79 ft/yr (24m/yr). After construction of the first jetties in 1940, this rate gradually decreased to 25 ft/yr (8 m/yr) by 1974. Most littoral material bypasses the jetties due to inefficient orientation to the present shore line. Field tracking of subsurface floats provided data to calibrate a small, distorted-scale model.