THIN LAYER PLACEMENT
The elevation and geomorphology within tidal salt marsh platforms determines the overall health of marsh vegetation . Furthermore , wetland vegetation facilitates the vertical accretion of the marsh through increase in root mass and the deposition of organic matter into sediments . This ecological mechanism allows for marshes to adapt to changing environmental conditions related to tidal fluctuations and sea level rise . While this adaptation of the marsh platform occurs naturally , there are concerns regarding whether the rate of sea level rise outpaces the natural ability for marshes to vertically accrete sediments . This has initiated efforts to look into human interventions to increase marsh elevations .
THIN LAYER PLACEMENT
Thin-layer placement of sediment ( TLP ) is one of the primary strategies used by federal and state agencies to increase the elevation of the marsh platform . TLP mimics the natural process of vertical accretion through the artificial introduction of sediment , often with dredged material , to the marsh surface . This involves depositing thin layers of sediment , usually by spraying a sediment slurry under high pressure directly over the marsh surface . In addition to increasing the vertical elevation of marshes , the added sediment encourages marsh re-vegetation , as well as increases in marsh biomass , plant stem density , and nutrient uptake into plant tissue , as long as sulfuric acid content is mitigated ( National Estuarine Research Reserves System [ NERRS ], 2020 ). Sulfur is extremely important to the marsh environment as it acts as the major electron receptor for respiration in anoxic marine sediments ( Howarth , 1984 ). TLP is a practice that is increasingly being used to assist marsh habitat in adapting to sea level rise ( NERRS , 2020 ). This strategy can also be used to mitigate issues related to geomorphology and reduced ability for marshes to properly drain tidal saltwater .
Figure 45 : Diagram of thin layer placement function to support marsh resilience ( NOAA , 2020 ).
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