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Mounds View Stormwater Pond Assessment <br />2 METHODS <br />July 2023 <br />2.2.3 DESKTOP ANALYSIS OF SEDIMENTATION <br />Stantec used ArcGIS Pro software to process the GPS data collected during the field surveys to estimate <br />the sediment deposition in each basin. Each survey point collected was geographically referenced with a <br />corresponding elevation. Survey points used in the sedimentation analysis represent water surface <br />elevations, depth to sediment, depth to refusal transects, and upslope areas. Figure 2-3 shows an <br />example of survey points collected for a pond in the City. <br />Figure 2.3 Merged Dataset of Field -Collected Survey Data <br />These data were combined with data from a digital elevation model to create Triangulated Irregular <br />Networks (TINs) for both current conditions and assumed as -built conditions. TINs are surfaces created in <br />GIS from surveyed points. These surfaces are made by interpolating elevations between the elevations of <br />known input points. The two surfaces created for our analysis are made from the top of sediment depths <br />and refusal depths from the surveyed points. These were used to create bathymetry maps for the ponds. <br />Figure 2.4 shows an example bathymetry map for a pond in the City. Bathymetry maps for all ponds <br />surveyed are contained in Appendix B. The differences between the existing conditions and depth to <br />refusal TINs were used to estimate the accumulated sediments and total basin volumes. <br />10 <br />