Harris Lake Wetland Identification



This purpose of this assignment was to perform a spatial analysis on the 1,267 acre Harris Research Tract in southwest Wake County and map potential wetland areas. This research tract is collectively managed by Progress Energy and NCSU and used for research studies including longleaf pine restoration, timber production, and ecological research. To identify the potential wetland areas, a Topographic Relative Moisture Index (TRMI) was derived. TRMI is a scalar index that combines the elevation-derived landscape parameters into one grid data layer with cell values representing 'dry' to 'wet' conditions.


This assignment was part of the requirements for GIS 510, Introduction to Geospatial Information Science. All data required was provided with the assignment and included shapefiles for the study area, the Harris boundary parcel, and the Hydrology of the area. In addition to the shapefiles, the landscape parameters and reclassification tables used to calculate the TRMI value were also provided.


The Topographic Relative Moisture Index (TRMI) is a combination of four elevation derivatives: slope steepness, aspect, relative slope position, and slope configuration. The general approach was to calculate the landscape parameter of interest (slope, aspect, etc.) based on a cells spatial relationship with neighboring cells and then re-classify the output a new value reflecting the potential wetness.

This process involved converting the hydrology shapefile to a raster and reclassifying the cell values to represent either water or no water. This reclassified raster was then used as a mask to effectively remove existing cells representing water from the other data layers via the Raster calculator. Then, the resultant layers could be summed via the Raster calculator to obtain the TRMI index value for the remaining cells of the study area.


The techniques used in this exercise can be to reduce cost prior to beginning field studies or data collection. By first eliminating areas that do not apply to the goals of the project, resources can then be focused on the pertinent areas of interest and thus eliminate unnecessary field time and labor costs associated with the work. This can be especially important when working in remote areas when labor costs and transportation time to the study area can be one of the most expensive aspects of the project.