The following processing stepswereperformed by Neil Ganju using VDatum online (VDatum ver.3.9) and Matlab (ver.2018a).
a) Convert elevations from the North American Vertical Datum of 1988 (NAVD88)to Mean Tide Level (MTL) referenced elevations.
Upload the ASCII file of latitude and longitude coordinates and elevation to VDatum online , and transform vertical datum from the NAVD88 to MTL. Do this for the marsh unit elevation and elevation of the vegetated part of the marsh unit to calculate mu_ELEV_MTL and vg_ELEV_MTL, respectively. Use value from the nearest Vdatum point for any point where VDatum has no data.
b) Calculate sediment budget from UVVR based on Ganju and others (2020) with SB= -0.416*log(UVVR)-1.0749, where SB is sediment budget in kilograms per square meter per year, and log() indicates natural logarithm function.
c) Calculate total sediment flux with SF= SB*ATOT_M2, where SF is sediment flux in kilograms per year and ATOT_M2 is total surface area of marsh unit in square meters.
d) Calculate sediment flux for the three scenarios considered: Global mean sea level rise of 0.3 meters, 0.5 meters and 1.0 meters by year 2100.
Sea-level rise (SLR) reduces vegetated marsh area, therefore, causes reduction in sediment flux. The sediment flux under SLR is calculated with SF_SLR= (SB-(GMSLR-BGRND_RSLR)*RHO_F)*ATOT_M2, where SF_SLR is sediment flux under SLR, RHO_F is dry bulk density of future deposited sediment, GMSLR is the local SLR in meters for a specific global mean sea level rise scenario, and BGRND_RSLR is the non-climatic background relative sea level rise in meters. RHO_F was assigned 159 kilograms per cubic meters from Morris and others (2016). For sea level rise projections, the averages of values from two stations (LEWES and KIPTOPEKE) from Sweet and others (2017) were used: 0.00175 meters for BGRND_RSLR, 0.0051, 0.0066, and 0.0132 meters for GMSLR of 0.3, 05. and 1.0 meters by 2100.
e) Total sediment mass in the vegetated plain above MTL is calculated with TS= vg_ELEV_MTL*AVEG_M2*RHO_E, where TS is total sediment mass, AVEG_M2 is the surface area of the vegetated part of the marsh unit and RHO_E is the dry bulk density of existing marsh substrate sediment. RHO_E was assigned 373 kilograms per cubic meters from Morris and others (2016).
f) Calculate lifespan (in years) for the background relative SLR with the equation BGRND= -TS/SF. Calculate lifespan (in years) under the global mean sea level rise by 0.3 meters, 0.5 meters and 1.0 meters by year 2100 scenarios with the equation GMSL= -TS/SF_SLR for each scenario (GMSL03, GMSL05, GMSL10, respectively).
g) Save results as a Matlab data file [ASIS_life.mat].
Morris, J.T., Barber, D.C., Callaway, J.C., Chambers, R., Hagen, S.C., Hopkinson, C.S., Johnson, B.J., Megonigal, P., Neubauer, S.C., Troxler, T., and Wigand, C., 2016. Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state. Earth's future, 4(4), 110–121. https://doi.org/10.1002/2015EF000334
Sweet, W.V., Kopp, R.E., Weaver, C.P., Obeysekera, J., Horton, R.M., Thieler, E.R., and Zervas, C., 2017, Global and regional sea level rise scenarios for the United States (Tech. Rep. NOS CO-OPS 083). Silver Spring, MD: National Oceanic and Atmospheric Administration. https://doi.org/10.7289/v5/tr-nos-coops-083