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A Geospatial Methodology for Mapping Land Parcels with Individual On-Site Wastewater Disposal Systems
Proceedings of the 2022 Mississippi Water Resources Conference

Year: 2022 Authors: Cartwright J., Grala K., Collini R.

Individual on-site wastewater disposal systems (IOWDS) or septic systems are an ever-increasing source of non-point source pollution along the coast of Mississippi. Inventories of these systems are not always complete or simply non-existent. This project utilized geospatial technologies, specifically geographic information systems (GIS), to identify land parcels that are potentially using an IOWSD. The approach used existing service utility provider records, land parcels, and improvement values to identify properties that are likely to have on-site waste disposal for a specific service area. The methodology was developed around geocoding techniques coupled with multi-criteria selection for property identification. The project area had a total of 83,863 parcels and 22,976 were identified as non-serviced parcels. Using a threshold improvement value of $7,500 resulted in 9,550 parcels that potentially have an IOWDS. These identified parcels were assessed for vulnerabilities based on groundwater depth, high-tide flooding for current and future sea level rise, and current and future storm surge under future sea level rise scenarios. 6,232 (65%) of these were found to be at some level of risk over the next several decades due to changes in groundwater, high tide, and/or storm surge as seas rise. Additional spatial analyses were performed and identified 1,621 parcels were near existing infrastructure to help prioritize transitioning from on-site disposal to a service utility.

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