*3.2. Development of Watershed Delineation*

The watershed delineation process is fundamental for the overall characterization to define the watershed boundaries and subwatersheds within each watershed. Generally, the watershed slopes from west to east through the heart of the LRGV, with an average slope of fewer than 0.3 m per kilometer [34]. Overall, its flat terrain varies from 0 m to 100 m. The resolution of the elevation raster-files was changed from 1 m to 60 m, which contributed to the reduction of file size and thus provided an efficient analysis. Since watershed delineation is key for this study, an ample watershed delineation was implemented to better assess the drainage areas of the watersheds. Previous studies have shown positive results for DEM reconditioning in watershed delineations in flat terrains [14]. Moreover, the assessment of satellite data and National Hydrography Dataset (NHD) was considered when evaluating the waterways and other laterals for the process. The satellite data were used to determine the accuracy of the location of the North and Central waterways. The NHD flowlines were used to determine the addition of laterals that could potentially drain into the waterways. LIDAR elevation data were reconditioned by developing several rasterelevation files to incorporate waterways into the data. This processing refers to burning waterways because the elevation data are not able to detect the waterways (Figure 2). Burning waterways consist of a rasterized version of the digital vector file to decrease the relative elevations of stream pixels by a uniform depth. Therefore, burning new channels

*Sustainability* **2021**, *13*, x FOR PEER REVIEW 6 of 23

the extent of the study area.

*3.2. Development of Watershed Delineation* 

study is that it portrays special features such as metadata, properties of the layers, and layer attributes to enhance watershed characteristics. The REON website was used to incorporate geospatial data and layers to show relative characteristics of the watersheds based on the watershed boundaries. To fully demonstrate watershed characteristics, the delineation of watershed boundaries was crucial for the assessment. Watershed delineation played an important role in this study, especially for the REON website to understand

The watershed delineation process is fundamental for the overall characterization to define the watershed boundaries and subwatersheds within each watershed. Generally, the watershed slopes from west to east through the heart of the LRGV, with an average slope of fewer than 0.3 m per kilometer [34]. Overall, its flat terrain varies from 0 m to 100 m. The resolution of the elevation raster-files was changed from 1 m to 60 m, which contributed to the reduction of file size and thus provided an efficient analysis. Since watershed delineation is key for this study, an ample watershed delineation was implemented to better assess the drainage areas of the watersheds. Previous studies have shown positive results for DEM reconditioning in watershed delineations in flat terrains [14]. Moreover, the assessment of satellite data and National Hydrography Dataset (NHD) was considered when evaluating the waterways and other laterals for the process. The satellite data were used to determine the accuracy of the location of the North and Central waterways. The NHD flowlines were used to determine the addition of laterals that could potentially drain into the waterways. LIDAR elevation data were reconditioned by developing several raster-elevation files to incorporate waterways into the data. This processing refers to burning waterways because the elevation data are not able to detect the waterways (Figure 2). Burning waterways consist of a rasterized version of the digital vector file to decrease the relative elevations of stream pixels by a uniform depth. Therefore, burning new channels into the DEM is an attempt to force alignment between topograph-

into the DEM is an attempt to force alignment between topographically derived flowlines and independently mapped hydrography [35]. ically derived flowlines and independently mapped hydrography [35].

**Figure 2.** Watershed delineation methodology. **Figure 2.** Watershed delineation methodology.

Once processing the LIDAR elevation data, the hydrology tools were used to develop elevation raster files such as fill, flow direction, and flow accumulation. Only three pour points were added manually to each corresponding waterway and then automated subwatersheds were developed. With the subwatersheds delineated, the overall watershed boundaries for the three watersheds were determined based on the flow accumulation lines. The flow accumulation lines correspond to the flow path for each watershed based on elevation data. The flow accumulation lines embody the actual waterways in mostly all the watersheds. The watershed boundaries correspond to the flowlines and follow an enhanced methodology for the type of terrain in the region. Once processing the LIDAR elevation data, the hydrology tools were used to develop elevation raster files such as fill, flow direction, and flow accumulation. Only three pour points were added manually to each corresponding waterway and then automated subwatersheds were developed. With the subwatersheds delineated, the overall watershed boundaries for the three watersheds were determined based on the flow accumulation lines. The flow accumulation lines correspond to the flow path for each watershed based on elevation data. The flow accumulation lines embody the actual waterways in mostly all the watersheds. The watershed boundaries correspond to the flowlines and follow an enhanced methodology for the type of terrain in the region.
