Accession Number:

AD1104150

Title:

Forces Driving the Morphological Evolution of a Mud Capped Dredge Pit, Northern Gulf of Mexico

Descriptive Note:

Journal Article - Open Access

Corporate Author:

NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS STENNIS SPACE CENTER United States

Report Date:

2018-07-28

Pagination or Media Count:

13.0

Abstract:

Sandy sediments preserved as paleo-channel fill on the inner shelf, some of which are overlain by modern muds, have been mined for barrier island restoration along the northern Gulf of Mexico. These mined areas have been termed mud-capped dredge pits. The processes governing the morphological evolution of the pits are poorly constrained due to limited observational data. Physical oceanographic e.g., currents and waves and sedimentary data were collected at Sandy Point dredge pit offshore Plaquemines Parish, Louisiana in summer 2015. Currents outside the pit flowed southward andor southeastward at speeds of 820 cms, while currents inside the pit had speeds less than 2 cms with no clear dominant direction. Wave heights detected inside the pit were less than 0.4 m. A high turbidity layer with suspended sediment concentration around 4 gL was observed above the pit floor, and its thickness was 0.5 m. With observational data as input, three2D numerical models were employed to predict pit morphological responses, including pit infilling, margin erosion and slope change. The model results suggest that resuspension events were rare on the seafloor adjacent to the pit under summer fair weather conditions. Modeled pit margin erosion was very limited. With little resuspension of seafloor sediment locally, weak margin erosion and stable pit walls, the dominant process governing pit evolution was infilling sourced by the deposition of suspended sediments from the Mississippi River plume.

Subject Categories:

  • Physical and Dynamic Oceanography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE