Evolution of Sand-Dominant Subaerial Phase, Atchafalaya Delta, Louisiana

Roberts, Harry H.; Adams, Roy D.; Cunningham, R.

doi:10.1306/2f918964-16ce-11d7-8645000102c1865d

Cited by 31 publications

(7 citation statements)

References 3 publications

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“…Therefore the effects of cold fronts on elevation loss are occurring to the same degree every year. This pattern of elevation loss, due to cold front seasonal forcings in the WLD and Atchafalaya Delta has been reported in a number of other studies (Rouse et al 1978;Kemp et al 1980;Roberts and Adams 1980;Mossa and Roberts 1990). This has important implications for land building capacity of this type of system as the need to offset this annual elevation loss is critical for continual net elevation gain.…”

Section: Elevation Loss Due To Cold Front Passagesupporting

confidence: 80%

“…However the majority of the fine grain sediment bypassed the bay and was deposited on the continental shelf prior to the early 1970s (Shlemon 1975). Small subaerial bars that first began to appear in the WLD in 1973 grew rapidly following high river flooding and infilling of shallow lakes upstream and adjacent to the WLO (Roberts and Adams 1980;Wellner et al 2005). Due to its unique occurance as a constructed river outlet that has been allowed to build land under natural hydrologic conditions, this system represents an extremely valuable analogue to many MRD coastal restoration strategies, which propose diverting river water and sediment into shallow coastal basins to reduce present wetland degradation rates (Parker and Sequeiros 2006;Kim et al 2009;Allison and Meselhe 2010;Paola et al 2011;CPRA 2012).…”

Section: Study Area and Seasonal Intervalsmentioning

confidence: 99%

“…Large river floods generally result in appreciable land building along the remaining unleveed Mississippi River distributaries, and account for the majority of land building observed in deltaic wetlands (Rouse et al 1978;Roberts and Adams 1980;Majersky et al 1997). The loss of flood derived overbank sedimentation is a major factor in increasing rates of wetland subsidence and land loss within the MRD (Baumann et al 1984;Day et al 2007;Day et al 2008;Syvitski et al 2009;Vörösmarty et al 2009).…”

Section: Introductionmentioning

confidence: 99%

“…No significant variation in frequency or timing of cold fronts occurs between years, therefore their effect on coastal processes is expected to be consistent year to year (Hardy and Henderson 2003). The pre-frontal phase, typically 24-48 hours before the front passes, is defined by strong southerly and easterly winds, producing waves and currents that push water toward the coast, resulting in water level increases of 0.5 to 1 m over predicted levels and resuspension of sediment from coastal bays and low organic matter deltaic wetlands (Rouse et al 1978;Roberts and Adams 1980;Mossa and Roberts 1990;Feng and Li 2010;Li et al 2011). As the front passes the coastal zone there is a sudden decrease in barometric pressure and an increase in precipitation and wind speed.…”

Section: Introductionmentioning

confidence: 99%

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Contribution of river floods, hurricanes, and cold fronts to elevation change in a deltaic floodplain, northern Gulf of Mexico, USA

Bevington

Twilley

Sasser

et al. 2017

Estuarine, Coastal and Shelf Science

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Deltas are globally important locations of diverse ecosystems, human settlement and economic activity that are threatened by reductions in sediment delivery, accelerated sea level rise, and subsidence. Here we investigated the relative contribution of river flooding, hurricanes and cold fronts on elevation change in the prograding Wax Lake Delta (WLD). Sediment surface elevation was measured across 87 plots, eight times from February 2008 to August 2011. The high peak discharge river floods in 2008 and 2011 resulted in the greatest mean net elevation gain of 5.4 to 4.9 cm over each flood season, respectively. The highest deltaic wetland sediment retention (16.3% of total sediment discharge) occurred during the 2008 river flood despite lower total and peak discharge compared to 2011. Hurricanes Gustav and Ike resulted in a total net elevation gain of 1.2 cm, but the long-term contribution of hurricane derived sediments to deltaic wetlands was estimated to be just 22% of the long-term contribution of large river floods. Winter cold front passage resulted in a net loss in elevation that is equal to the elevation gain from lower discharge river floods and was consistent across years. This amount of annual loss in elevation from cold fronts could effectively negate the long-term land building capacity within the delta without the added elevation gain from both high and low discharge river floods. The current lack of inclusion of cold front elevation loss in most predictive numerical models likely overestimates the land building capacity in areas that experience similar forcings to WLD.

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Section: Elevation Loss Due To Cold Front Passagesupporting

confidence: 80%

Section: Study Area and Seasonal Intervalsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Contribution of river floods, hurricanes, and cold fronts to elevation change in a deltaic floodplain, northern Gulf of Mexico, USA

Bevington

Twilley

Sasser

et al. 2017

Estuarine, Coastal and Shelf Science

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“…The fourth change to the system that could influence f A is the growth of the large deltas in Grand Lake in the Atchafalaya Basin ("Deltas" Region, Figure 1b). Between 1916 and 1950, about 180 km 2 of lacustrine delta deposits accumulated, largely filling the ∼3 m deep Grand Lake (Roberts et al, 1980;Tye & Coleman, 1989). While natural channels formed during this accumulation, channelization was dominated by the dredged CPC (Figure 1e).…”

Section: Factors Potentially Influencing Partitioningmentioning

confidence: 99%

Influences on Discharge Partitioning on a Large River Delta: Case Study of the Mississippi‐Atchafalaya Diversion, 1926–1950

Shaw

Mason

et al. 2021

Water Resources Research

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Artificial bifurcation effect on downstream channel dynamics of a large lowland river, the Atchafalaya

Wang

et al. 2021

Earth Surf Processes Landf

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Artificial river bifurcations have been widely created for different purposes. Yet, long‐term dynamics in the bifurcated channels and natural channels downstream of the artificial bifurcation nodes are not well investigated. Herein, we employed an approach combining three decades (1977–2006) of bathymetric survey records, geographic information system (GIS) application, and bed material transport modeling to investigate riverbed dynamics in an artificially bifurcated channel and the downstream natural channel of the Atchafalaya River, the largest distributary of the Mississippi River. Decadal changes in the riverbed volume were determined, and erosion/deposition patterns in these channels were assessed. Hydraulic properties under low, medium, and high flow conditions were quantified to analyze main factors affecting the long‐term trend of channel dynamics. Our study found that flow from the Atchafalaya River into the artificially bifurcated Wax Lake outlet channel (WLOC) steadily increased. Hydraulic gradient, stream power, and shear stress under all flow conditions of the WLOC were greater than those of the Atchafalaya River natural mainstem channel (ARMC) downstream of the artificial bifurcation. On average, 52% of the total bed material loads (BMLs) from the Atchafalaya entered the steeper and straight WLOC with 41% of the river's flow from 1977 to 2006. Despite the higher sediment inflow, the WLOC degraded with an average rate of −0.12 × 105 m3 km−1 yr−1, while the ARMC downstream of the bifurcation aggraded substantially with an average rate of 0.38 × 105 m3 km−1 yr−1 over the three decades. The disproportional flow–sediment ratio and channel erosion‐aggradation patterns below the artificial bifurcation were apparently a reflection of the difference in the river hydraulic properties. These findings imply that lowland alluvial river diversions for introducing sediment to build new land in world's sinking deltas need to develop sustainable solutions in order to avoid causing severe bed scouring in one but excessive deposition in the other channel downstream of the bifurcation.

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Evolution of Sand-Dominant Subaerial Phase, Atchafalaya Delta, Louisiana

Cited by 31 publications

References 3 publications

Contribution of river floods, hurricanes, and cold fronts to elevation change in a deltaic floodplain, northern Gulf of Mexico, USA

Contribution of river floods, hurricanes, and cold fronts to elevation change in a deltaic floodplain, northern Gulf of Mexico, USA

Influences on Discharge Partitioning on a Large River Delta: Case Study of the Mississippi‐Atchafalaya Diversion, 1926–1950

Artificial bifurcation effect on downstream channel dynamics of a large lowland river, the Atchafalaya

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