Effect of weirs on sediment deposition in Louisiana coastal marshes |
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Authors: | Denise J Reed |
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Institution: | (1) Louisiana Universities Marine Consortium, 70344 Chauvin, Louisiana, USA |
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Abstract: | Sediment deposition both inside and outside of fixed-crest weirs was measured for fresh/intermediate, brackish, and saline
marsh areas in coastal Louisiana, USA. Sediment traps, collected on a weekly basis, were used to monitor short-term changes
in sediment deposition. Feldspar marker horizons were used to measure cumulative marsh accretion during the 16-week monitoring
period. Results show that for most sites less sediment is deposited in marsh behind weirs than at the control sites outside
the weirs. Patterns at each site are consistent throughout the 16 monitoring periods. At only one site was no significant
difference found. Streamside areas both inside and outside the weirs were found to have higher rates of sediment deposition
than backmarsh areas. At both marsh locations, sediment deposition rates were higher outside the weirs than inside. More sediment
was deposited in saline marshes than in brackish or fresh/intermediate areas. The vertical accretion data shows that marshes
in most areas are accreting sufficiently rapidly to keep pace with local rates of sea-level rise, except for two areas, both
of which are inside weirs. |
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Keywords: | Marsh management Weirs Sediment deposition Coastal marshes Louisiana |
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