4.0 APPENDIX (Tool Workflow and Use)

The following sections describe the overall workflow for running the tool, along with details on the inputs and outputs of the tool. This tool works with any version of ArcPro; it does not work with ArcMap.

2D FLOOD PROFILE DECISION MODEL WORKFLOW:

1. If not already available, export the 1% annual chance WSEL grid from HEC-RAS.
2. Load the following input files to your map document:

• HEC-RAS 1% WSEL grid from previous step
• S_XS / Evaluation Lines (if applicable) for the stream you are testing
• S_BFE (if applicable) for the stream you are testing
• Dissolved (except static BFE polygons) Zone AE/AH floodplain for the stream you are testing

3. Add the Python Toolbox to your project catalog: FEMA_R8_SID_128_Check.pyt

Figure 3. Example of the Toolbox added to the ArcPro Catalog

4. Open the SID 128 2D Test tool and insert applicable files into the parameters and set output file location. See “Tool Inputs” and Figure 4 below for more details.
5. Run the tool. Tool processing steps are reported in the Messages dialog box.
6. Examine the output file “Results.txt”. If the stream failed, examine the output results (S_ S_Test_Centroid_Features.shp) to determine where extra BFE or Evaluation Lines are needed. See “Output Files” below for more information on output files.
7. If needed, place exclusion polygons around points that should be excluded from the test. See “Exclusion Polygons” for more information on exclusion polygons.

TOOL INPUT:

See Figure 4 for the tool’s input parameters. At least one WSEL input parameter from either 1 (S_XS) or 2 (S_BFE) is required for the tool to run. These do not need to be in the FEMA DCS schema at this time, only the water surface elevation (WSEL) is required to be populated. Each 2D modeled flooding source is required to be evaluated individually. If multiple flooding sources are modeled together, this might require the data be divided into individual files for each flooding source. Table 2 describes the tool’s inputs for each flooding source evaluated. All input files are required to be submitted in the SID_128_Check folder as indicated in the “Documentation” section above.

Figure 4. Toolbox Input Parameters

Table 2. Toolbox Input Parameters

TOOL OUTPUT:

See Figure 5 for the list of output files that are generated from the tool. The following lists what each file represents and information within each file. All output files are required to be submitted in the SID_128_Check folder as indicated in the “Documentation” section above.

Figure 5. Tool Output Files (*these output files are only included if exclusion areas are provided as input)

1. S_Test_Centroid_Features.shp: This is a point shapefile that is created by the tool. The tool creates a point inside the center of the 50-foot resolution grid index (S_Test_Centroid_Features.shp) then extracts the WSEL from the HEC-RAS WSEL grid and the interpolated SFHA WSEL grid at each point and stores the WSEL as attributes (see Table 3 below). The tool calculates the difference between those two elevations at each point and stores the result into another attribute. Lastly, an attribute is populated whether the difference is within the 0.1-foot tolerance, indicating if it is passing or failing the check. If the point is attributed as “Missed”, that means there was not a difference calculated because one of the WSEL surfaces had a null value3. The user can symbolize by the “valid_diff” field to determine areas where additional BFE or evaluation lines are needed to improve the accuracy.

Table 3. Attribute Descriptions of the S_Test_Centroid_Features.shp

2. S_Test_Index_Features.shp: This is a polygon feature of the 50-foot grid index created by the tool. A 50-foot grid index is created around the extent of the input S_Fld_Haz_Ar and then intersected with the shape of the S_Fld_Haz_Ar. The test points are then placed at the centroid of the intersected grid index.
3. S_WSEL_Lines.shp: This is a line feature of the combined input cross-sections and BFE lines. This is the feature that is used to create the SFHA_WSEL.tif.
4. SFHA_WSEL.tif: This is a raster that is developed by the tool input cross-sections, BFE lines, and if applicable static BFE.
5. Results.txt: This is a text file that displays the summary results of the SID 128 Check tool. It notes the mesh (grid index) test size, and the vertical test tolerance. The results note how many test points were created, and how many were missed. If more than 10% were missed, the tool will fail the study and the results will state: "Missed Percentage too High (more than 10%), Failed". The results summary then notes how many valid points (not missed) and how many pass or fail, along with the percentage. Additionally, a statement is given if the study passes or fails based on the BFE accuracy standard noted in Table 1 and Table 4. Lastly, if exclusion areas are provided as input, the results will show the comment provided in the exclusion polygon attribute table and the number of points excluded for each unique comment.

Table 4. Study Pass/Fail Percentage and Results.txt Message

6. Additional Output Files if Exclusion Areas are Used in Input:

• S_Exclusion_Areas: A copy of the input exclusion area polygon feature
• S_Test_Centroid_Features_Select: A selection of the test points that do not include points within the exclusion areas.