Comment:

The SLAMM salinity model estimates a spatial map of salinity under conditions of low tide, mean tide, high tide, and flood tide (water at “salt elevation”). Considerations of salinity may be required when modeling marsh fate as marsh-type is often more highly correlated to water salinity than elevation when fresh-water flow is significant (Higinbotham et. al, 2004). Predicted salinity may also have effects on accretion rates. The SLAMM model attempts to predict mean salinities without the requirement for input-data-intensive and computationally-intensive three dimensional hydrodynamic models. In the near future, a capability to link the SLAMM model to spatial model output from more complex salinity models will be released as part of SLAMM 6. The existing SLAMM model remains fairly experimental and simple in nature, though it has successfully been calibrated to salinity data in Georgia and Washington State. The SLAMM salinity model assumes a salt wedge setup within an estuary. Water heights are estimated as a function of tide range, mean tide level, fresh water flow, and calculated fresh water retention time. The depth of the salt wedge is estimated as a function of river mile, the slope of the salt wedge, and the tide level, and sea level rise. After an initial condition has been successfully captured, the model may be run with an increased sea level to predict the salinity changes under this condition. The model has been calibrated to effectively capture salinity variations under existing conditions but validation of model predictions under conditions of SLR has not yet been undertaken.