GIS Modelling of Intertidal Wetland Exposure Characteristics
Journal of Coastal Research, Volume 27, Issue 6A), November 2011: 44-51
Nathan Crowell, Timothy Webster, and Nelson J. O’Driscoll
“Exposure to solar radiation and tidal inundation are important factors for a wide variety of chemical and ecological processes in coastal ecosystems. Accurate quantification of these factors is often difficult on a local scale. To address this research gap, a remote-sensing approach was developed to model inundation and radiation characteristics within an intertidal zone located in the Minas Basin (Bay of Fundy, Nova Scotia, Canada). A light detection and ranging (LIDAR)–derived elevation model was subjected to tidal modelling based on hourly sea level predictions and solar modelling based on sunrise and sunset times for 2009. Model results indicated an intertidal zone of 145.8 km2 with an elevation between −6.9 m and 6.8 m. The intertidal zone was determined to contain three unique wetland classes: (1) 4.4 km2 of high salt marsh, dominated by Spartina patens; (2) 5.0 km2 of low salt marsh, dominated by Spartina alterniflora; and (3) 63.1 km2 of nonvegetated marine flat (73.3 km2 unclassified intertidal).
Orthorectified imagery for a region of intertidal wetland separated from agricultural land by a protective dyke to the NE of Wolfville, Nova Scotia, Canada taken in 2006. The model results were overlaid to depict (B) delineated wetland classes based on dominant vegetation, (C) atmospheric exposure characteristics of the intertidal zone based on hydrographic modelling which examined topography and hourly tidal predictions for 2009, and (D) solar exposure characteristics of the intertidal zone based on hydrographic modelling and astronomical predictions.
“Detailed exposure characteristics were calculated for each of the classes within the intertidal zone at 10-cm vertical intervals. Exposure calculations for 2009 showed that an average of 4.2 km2 of salt marsh were exposed to solar radiation and 8.4 km2 were exposed to the atmosphere each hour. Similarly, 11.7 km2 of marine flat were exposed to solar radiation and 22.9 km2 were exposed to the atmosphere each hour. The developed remote-sensing techniques successfully established intertidal zones, uniquely identified wetland classes, and modelled inundation and solar exposure characteristics within the study area.”
