IMS Models

Interactive Mapping Sites are appearing at an explosive rate across the internet, and represent a rich niche for GIS expertise to fill.  The following websites will be studied as models upon which to base the design of the HCA IMS:

• United States Geological Survey (USGS) – 

• City of San Antonio –

• City of New Braunfels –


The USGS site is a viewer on a national (and in some cases international) scale.  There is an abundance of data, but due to the scale of the site, it is not feasible to include many of the environmental features that are requested by HCA.  The city websites are more local in scale, but again, many environmental features are missing.


Groundwater Vulnerability Models

There are several existing GIS models which have similar purposes to this study.  One model (Hammond, Jr. and Hardberger) studies the impact of population growth, impervious cover, and their effects on the Trinity Aquifer recharge quantities as they relate to precipitation.  In another study (Stone and Schindel, 2002), a GIS matrix was developed and applied to the process of prioritizing sensitive karst lands.

Finally, DRASTIC is a model used to determine the vulnerability of an area to groundwater contamination (Aller et al., 1987).  Each of seven hydrogeologic factors is separately evaluated and ranked on its own scale, then weighted and combined with the other factors to produce an index.  In GIS terms, each component is represented by a separate data layer, which can then be rasterized and reclassified, and a final index layer produced via raster calculation.

All of these models are relevant to our project, although the DRASTIC model most resembles the one being utilized by the HCA.




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