Volume 8, Issue 3 (March 2011)
The Use of Topography as an Indicator of Ground Water Flow Direction and Its Implications for Due Diligence
Topography often is used as a quick and preliminary method to identify local and regional ground water flow patterns within the upper-most saturated interval. This approach usually is applied in designing shallow monitoring networks at properties or in areas where little to no site specific hydrogeologic data are available. Perhaps the most problematic application of this method is in due diligence. Critical business decisions regularly are made based on potential environmental impacts from surrounding parcels using topographic presumptions about upgradient or downgradient ground water flow directions. However, what most practitioners fail to realize is that topography is a reliable predictor of ground water flow only under a fairly narrow range of physiographic conditions. To assist in determining when topography should be used to evaluate ground water flow direction within the upper-most saturated interval, we have developed an evaluation matrix that allows the investigator, who may have only modest hydrogeologic training, to rapidly identify when topography can be appropriately and reliably used to determine shallow ground water flow directions. Limitations on the use of the matrix are provided as well as suggestions for obtaining site specific data that allow for a more definitive understanding of shallow ground water flow without the need for intrusive field work.