I am new to this forum and this is my first post here, so I hope I am in the right place.
The overall objective is to determine the proximity of water-supply wells in the Virginia Coastal Plain to the groundwater saltwater-transition zone. The first figure below illustrates a series of rasters that represent the transition zone as chloride iso-concentration surfaces. The second figure shows spatial relations of a withdrawal well to the chloride surfaces. Vertical proximity is the length of penetration of the well below each of the surfaces. Horizontal proximity is the distance of the well to higher-concentration surfaces.
Extract Values to Points has completed the first step of analysis. The wells are in GIS as points. Extract Values to Points determined vertical proximities by obtaining the elevation of each chloride surface at each well, from which length of penetration was calculated using point data on well depths. The third figure here summarizes penetration below the 50mg/L chloride surface. The raster is shown with shading along with corresponding elevation contours (obviously a lot more complex than the first two figures here convey). Wells are classified by length of penetration. They tend to penetrate deeper where the chloride surface is shallow to the east. Some very deep wells to the west, however, also penetrate deeply even though the surface there is deep. Similar maps have been produced for other higher-concentration chloride surfaces.
I have been looking among the various GIS tools but am unable to find anything that would clearly provide me with a measure of horizontal proximity. My conceptual approach is the same as for vertical proximity, but so far without any corresponding analytical approach. Any feedback would be appreciated.
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