Fluvial Sand Sources for Barrier Island Restoration in Louisiana: Geotechnical Investigations in the Mississippi River

Abstract

I FINKL, C.W.; KHALIL, S.M.; ANDREWS, J.; KEEHN, S., and BENEDET, L., 2006. Fluvial sand sources for harrier island restoration in Louisiana: geotechnical investigations in the Misaisaippi River. Journal of Coastal Research, 22(4), 773-787. West Palm Beach (Florida), ISSN 0749-0208,Coastal land loss in the Mississippi River delta region, related to degradation of wetlands and erosion of barrier islands, contributes to loss of valuable habitat, endangerment of infrastructure and sodoeconomic systems, and coastal flooding hazards. Restoration of theae ecosystems is thus a primary activity that requires large volumes of sand to rebuild heach-dune systems and restore wetland habitats. Sand sources have traditionally heen sought offshore in the marine environment, hut there are problems associated with aethacks from oil and gas infrastructure, presence of muddy overburden, and limited reserves of heach-quality sediments. Fluvial aand sources in channel and point-bar deposits become an attractive alternative for barrier island restoration because of large volumea of relict deposits and because active sand waves are renewable. Results of preliminary geophysical and geotechnical investigations in the lower Mississippi River (south of New Orleans) along a 32-km stretch of the river indicate the presence of at least 23 million cuhic meters of usable sedimenta in seven potential borrow sitea. Caveata to asaesament and exploitation of river sands include interpretation of vihracores and seismic reflection profiles that include evidence of lateral translation-type bank failures along bendways, lateral alumpa, and postdepositional disturbance of strata above -30 m. Reliable extraction of good quality sediment should occur down current from bendways. ADDITIONAL INDEX WORDS: Sand search, fluvial sand resources, river mining, renewable sand resources, barrier islands, beach erosion.

The lowermost Mississippi River: a mixed bedrock‐alluvial channel

“…The difference between the means of the two regression lines provides a characteristic depth difference between alluvial sediments and substratum and can be used to approximate the thickness of alluvial cover over the substratum for a given location; this value is 0 to 15 m, increasing slightly downstream from RK 130 to RK 35. The scatter in the data about the regression lines, however, shows that locally the depth differences between ‘alluvial sand’ and ‘channel‐bottom substratum’, and therefore the alluvial sediment thickness, can vary from no cover to up to 25 m. These observations confirm those by Finkl et al. (2006), who report sand thickness ranging from 3 to 20 m based on vibracores collected from channel bars between RK 30 and RK 45.…”

“…Proposals to rebuild the deteriorating Louisiana coastal wetlands and barrier islands require sediment from the Mississippi River (e.g. Finkl et al. , 2006).…”

Challenges of ecosystem restoration in Louisiana – availability of sediment and its management

“…Sand bars located in hydro-geomorphological settings (river meander point bars) have the added advantage of being naturally replenished by fluvial deposition of traction bedload. Due to the thickness of these river sands, large volumes are potentially available for coastal restoration (Finkl et al, 2006). A first-order assessment of Mississippi River sand volumes was developed, with a total sand volume from river mile 70 to Head of Passes (Fig.…”

Artificial modifications of the coast in response to the Deepwater Horizon oil spill: quick solutions or long‐term liabilities?

“…Offshore sandy sediment resources are limited in extent and volume (Kulp et al . 2005), and the transport of suitable sediment from farther afield (Finkl et al . 2006) can be prohibitively expensive in terms of both time and resources.…”

“…Sediment is precious in this region and should be used strategically (Kulp et al . 2005; Finkl et al . 2006).…”