Watershed Modeling System

Watershed Modeling System WMS v8.0 MARICOPA COUNTY TUTORIALS

TABLE OF CONTENTS 1 MARICOPA COUNTY: NFF AND HEC-1... 1-1 1.1 OBJECTIVES... 1-1 1.2 DELINEATING THE WATERSHED... 1-1 1.3 BUILDING THE NFF SIMULATION... 1-5 1.4 BUILDING THE HEC-1 SIMULATION... 1-8 1.5 SAVE AND RUN THE HEC-1 SIMULATION... 1-14 2 MARICOPA COUNTY: MASTER PLAN CREATING A PREDICTIVE HEC-1 MODEL... 2-1 2.1 OBJECTIVES... 2-1 2.2 DEFINING THE WATERSHED... 2-1 2.3 BUILDING THE HEC-1 MODEL... 2-6 2.4 RUN HEC-1 FOR EXISTING CONDITIONS... 2-11 2.5 RUN HEC-1 FOR THE PROPOSED CONDITIONS... 2-11

1 Maricopa County: NFF and HEC-1 CHAPTER 1 Maricopa County: NFF and HEC-1 1.1 Objectives In this exercise, you will learn how to use WMS to set up and run HEC-1 and National Flood Frequency (NFF) simulations. The WMS customizations for drainage studies in Maricopa County will be highlighted. By following these exercises, you will learn how to: 1. Delineate a watershed using DEM data 2. Build a Maricopa County NFF simulation 3. Run NFF and view the results in WMS 4. Build a Maricopa County HEC-1 simulation 5. Run HEC-1 and view the results in WMS 1.2 Delineating the Watershed Before building a hydrologic model such as HEC-1, we need to define the watershed boundaries and calculate required parameters (such as basin area, surface slope, etc). This is done by importing a DEM and using the automatic basin delineation tools in WMS. 1. Close all instances of WMS

1-2 WMS Maricopa County Tutorials 2. Open WMS 3. Select File Open 4. Locate the folder C:\WMS80\tutorial\Maricopa\tut1 5. Open elevations.asc 6. Select OK to import the DEM 7. The DEM contours will be generated and displayed. In order to delineate watershed basins, we need to compute flow directions and flow accumulations for each DEM cell. 1.2.1 Using TOPAZ 1. Switch to the Drainage module 2. Select DEM Compute TOPAZ Flow Data 3. Change the input/output location if desired by clicking the browse button 4. Select OK 5. Select the Current Coordinates button 6. Change both Horizontal and Vertical units to U.S. Survey Feet 7. Select OK 8. Select OK 9. Select Close once TOPAZ finishes running (you may have to wait a few seconds to a minute or so) Flow directions and accumulations are now automatically read into WMS. The blue lines that appear on the screen represent anticipated stream locations. 10. Select Display Display Options 11. Choose DEM Data and set the Min Accumulation for Display to 0.09 12. Select OK

Maricopa County: NFF and HEC-1 1-3 1.2.2 Defining the Basins The first step in defining basins and sub basins is to place outlet points at the desired locations along the stream(s). Then, WMS will create stream arcs based on the outlet locations. Finally, basin boundaries are delineated based on the stream network and areas contributing to these streams. 1. Switch to the GIS module 2. Select Data Add Shapefile Data 3. Open basins.shp. This shapefile will act as a background image and help us to place the outlets. 4. Switch to the Drainage module To aid us in placing the outlet points, we will zoom in on a portion of the DEM. Then we will import a shapefile containing all of the watershed basins in Maricopa County: 5. Select the Zoom tool and draw a box around the area indicated by the rectangle in Figure 1-1 Figure 1-1: Zoom in on the area in rectangle. In order to make the screen less busy, we will hide the DEM contours. This will make it easier for us to place the outlets:

1-4 WMS Maricopa County Tutorials 6. Select Display Display Options 7. Choose DEM Data and toggle off the DEM Contours toggle box 8. Select OK 9. Select the Create Outlet Point tool 10. Create a point in each of the two locations shown in Figure 1-2. Be sure to place each point directly on a stream (zoom in if you need to). Figure 1-2: Approximate locations for placing the two outlets 11. Select DEM DEM -> Stream Arcs 12. Select OK to accept the default threshold value. This value is the minimum accumulation (in units of area) for creating stream arcs. In other words, for a DEM cell to be considered a stream cell, the upstream area contributing to that cell must be greater than or equal to the threshold value. 13. Select DEM Define Basins

Maricopa County: NFF and HEC-1 1-5 14. At this point you should see the creation of colored basin boundaries. If you see only one or no basins delineated, go back and verify that both outlet points are located directly on a stream cell (use the Zoom tool) and repeat the steps again. 15. Select DEM Basins -> Polygons 16. Select DEM Compute Basin Data 17. Select OK You have now delineated a watershed with two sub basins (corresponding to two outlets) and computed basin parameters to be used in a hydrologic model. You ll notice that in some areas, the DEM generated basin boundaries diverge from those of the shapefile. Such variations might be attributed to different dates of production for the DEM and shapefile, and/or limitations of gridded elevation data. 1.3 Building the NFF Simulation WMS includes an interface to the National Flood Frequency Program (NFF). The NFF program is a compilation of all the current statewide and metropolitan area regression equations, including equations specific to Maricopa County, AZ. We will be using the watershed developed in the previous section to run the NFF model. If you haven t already done so, copy the files evaporationgrid and MeanAnnualRainAsciiGrid to the same directory as your WMS executable. To begin, we will import a shapefile containing the NFF Regions of Arizona and map the regions to feature objects. These region polygons will be used by WMS to automatically set up the needed Regression Equations used by NFF. 1.3.1 Creating the NFF Regions Coverage Before adding another coverage, we will hide the basins.shp file to make the screen less cluttered: 1. Toggle off the check box next to basins.shp 2. Switch to the Map module 3. Create a new coverage by right-clicking on the Coverages folder in the Project Explorer and selecting New Coverage 4. Change the Coverage Type to NFF Region

1-6 WMS Maricopa County Tutorials 5. Select OK 6. Select File Open 7. Open arizusgs.shp 8. Switch to the GIS module 9. Select Mapping Shapes -> Feature Objects 10. Select Yes 11. Select Next > 12. Notice that the STATE and NFF_REGION fields are automatically mapped to the correct attributes 13. Select Next > 14. Select Finish 15. Switch to the Map module 16. Choose the Select Feature Polygon tool 17. Double-click on the polygon in the center, as shown in Figure 1-3, to verify that the State is Arizona and the Region is Central Arizona Region 12

Maricopa County: NFF and HEC-1 1-7 Figure 1-3: Double-click on the highlighted polygon to view its attributes 18. Select OK You have now created the NFF Regions coverage and can proceed to run the NFF computations. 1.3.2 Running NFF and Viewing Results 1. Select the Zoom tool and zoom in on the two sub basins, which currently appear as small gray circles, until they are distinguishable 2. Switch to the Hydrologic Modeling module 3. Change the Model list box (at the mid-top of the window) to NFF 4. Choose the Select Basins tool 5. Double-click the basin icon on the left, labeled 2B 6. Select Yes when asked if you want WMS to compute region areas, annual rainfall, and evaporation 7. Choose the Compute Results button WMS displays the peak flows for the various return periods in the window at the bottom of the dialog.

1-8 WMS Maricopa County Tutorials 8. Select Done 9. Double-click the basin icon on the right, labeled 1B 10. Select Yes 11. Choose the Compute Results button 12. In the output window at the bottom, click on the line for Recurrence [years] = 50 13. Choose the Compute Hydrograph button 14. Choose the Compute Lag Time Basin Data button 15. Change the method to Tulsa 100% Urban Method 16. Select OK twice 17. Select Done to exit the NFF dialog 18. Double-click on the hydrograph icon You have now computed peak discharge values for both basins and learned how to generate a hydrograph for any of the design storms using the NFF interface of WMS 19. Close the hydrograph plot window 1.4 Building the HEC-1 Simulation Now, we will proceed to set up the HEC-1 / Maricopa County parameters. Before we can run HEC-1, we need to define several required parameters, plus any optional parameters that we desire. We will define the following parameters in this portion of the exercise: Precipitation Losses Unit Hydrograph Method Routing (optional)

Maricopa County: NFF and HEC-1 1-9 1.4.1 Precipitation Data To input the Maricopa County precipitation data, we use the HEC-1 Job Control dialog: 1. Make sure the Models drop-down field at the top of the interface is set to HEC-1 2. Select HEC-1 Job Control 3. Choose the Initialize Maricopa County Precipitation Data button 4. Choose the Basin Average option and select 24-hour (storm duration) from the drop-down list 5. Click on the Browse button to select a rainfall grid to read in and use to compute precipitation 6. Open the file named noaa10y24h. This is a NOAA rainfall grid corresponding to a 10 year, 24-hour storm 7. Select OK to accept the default Rainfall computational cell size. Because the rainfall grid is approximately a 1 km grid size, no additional accuracy is achieved if the computational cell size is smaller than the default. 8. Select OK to close both dialogs The computed precipitation (centroid) is copied to the Basin Average parameter of HEC-1 1.4.2 Computing Losses Along with land use and soil type data, WMS can compute Loss Data based on the Maricopa County methodology. We will first import land use and soil type shapefiles and convert them to feature objects. Then, using a land use soil type look-up tables, we will compute the required Loss parameters. 1.4.2.1 Adding Land Use Data 1. Right-click on the Coverages folder in the Project Explorer 2. Select New Coverage from the pop-up menu 3. Change the Coverage Type to Land Use 4. Select OK 5. Switch to the GIS module

1-10 WMS Maricopa County Tutorials 6. Select Data Add Shapefile Data 7. Open landusewhitetanks.shp 8. Hide the NFF Region coverage by un-checking its box in the Project Explorer 9. Click the Frame macro in order to view the extents of the land use coverage. 10. Hide arizusgs.shp by un-checking its box in the Project Explorer, if you have not already done so If there are multiple shapefiles present in the Project Explorer of the GIS Module, then it is important to hide any and all shapefiles that you do not wish to map to feature objects. Since only visible shapefiles can be selected with the Select Shapes tool, you can hide all shapefiles but the one you are interested in, and then select the shapes you want to map to feature objects. Note, however, that if you do not use the Select Shapes tool to select the shapes that you want to map, then WMS will map all of the shapes from all of the shapefiles in memory, visible and hidden. 11. Select the Select Shapes tool 12. Draw a selection box around the two sub-basins, thereby selecting the land use polygons that cover your watershed 13. Select Mapping Shapes -> Feature Objects 14. Select Next 15. Find the column labeled LDUSE_LID and set its Mapping to Land use 16. Select Next 17. Select Finish 18. Switch to the Map module 19. Make sure the Land Use coverage is still the active coverage 20. Choose the Select Feature Polygon tool 21. Select Feature Objects Attributes 22. Under the Import land use attribute file section, choose Green-Ampt Parameter file 23. Click the Import file button

Maricopa County: NFF and HEC-1 1-11 24. Select OK to accept the warning message 25. Open landusemagtable.tbl 26. Toggle off the Display SCS CN s check box and toggle on the Display Green-Ampt Parameters box 27. Select Apply 1.4.2.2 Adding Soil Type Data 1. Right-click on the Coverages folder in the Project Explorer and select New Coverage 2. Change the Coverage type to Soil Type 3. Select OK 4. Switch to the GIS module 5. Select Data Add Shapefile Data 6. Open soilwhitetanks.shp 7. Hide landusewhitetanks.shp by un-checking its box in the Project Explorer If there are multiple shapefiles present in the Project Explorer of the GIS Module, then it is important to hide any and all shapefiles that you do not wish to map to feature objects. Since only visible shapefiles can be selected with the Select Shapes tool, you can hide all shapefiles but the one you are interested in, and then select the shapes you want to map to feature objects. Note, however, that if you do not use the Select Shapes tool to select the shapes that you want to map, then WMS will map all of the shapes from all of the shapefiles in memory, visible and hidden. 8. Select the Select Shapes tool 9. Draw a selection box containing the two sub basins 10. Select Mapping Shapes -> Feature Objects 11. Select Next 12. Find the column labeled SLTYP_LID and change its Mapping field to SCS soil type 13. Select Next

1-12 WMS Maricopa County Tutorials 14. Select Finish 15. Click anywhere outside of the soil type shapefile s boundaries to clear the selected polygons 16. Switch to the Map module 17. Choose the Select Feature Polygon tool 18. Double-click inside one of the soil polygons 19. Change the Import file type list box to Green-Ampt Parameter file 20. Click the Import file button 21. Select OK to accept the warning dialog 22. Open soiltable.tbl 23. Turn off the Display of SCS soil type box, and turn on the Display Green-Ampt parameters box 24. Select Apply 1.4.2.3 Computing Losses With the land use and soil type coverages defined, we are ready to compute Losses. To do this: 1. Switch to the Hydrologic Modeling module 2. Select Calculators Compute GIS Attributes 3. Change the Computation list box to Green-Ampt parameters 4. Make sure that you have read in both the Land use mapping and Soil type mapping tables. Choose the Land use mapping and Soil type mapping options to verify this, and click the Import button to load them if you have not done so already. 5. Select OK Based on the land use and soil type data, WMS now computes all the HEC-1 Loss parameters. We will now verify that the values were copied to HEC-1: 6. Double-click on either of the basin icons (brown box) 7. Click on the Precipitation button to verify that the rainfall has been properly mapped

Maricopa County: NFF and HEC-1 1-13 8. Select OK 9. Click the Loss Method button and view the Green-Ampt values computed from the land use and soil coverages. 10. Select OK 11. Select Done 1.4.3 Setting the Unit Hydrograph Method For this HEC-1 model, we will use the Clark Method to develop the Unit Hydrograph for both sub basins. To calculate these parameters: 1. Double-click on the basin icon (brown square) for the basin on the left 2. Click the Unit Hydrograph Method button 3. Choose the Clark (UC) option 4. Click the Compute Tc and R Maricopa County button 5. Set the Resistance coefficient roughness type to B-Moderately Low Roughness 6. Click the Compute Tc and R button 7. Select OK 8. Select OK again to return to the Edit HEC-1 Parameters dialog 9. Click the Next Hydrograph Station -> button twice to select the sub basin on the right 10. Click the Unit Hydrograph Method button 11. Choose the Clark (UC) option 12. Click the Compute Tc and R Maricopa County button 13. Select OK to the message stating that the slope is greater than allowed, and will be reset to 313 ft/mile 14. Change the Resistance coefficient roughness type to C-Moderately High Roughness 15. Click the Compute Tc and R button 16. Select OK

1-14 WMS Maricopa County Tutorials 17. Select OK 1.4.4 Specifying the Routing Method To simulate routing from the upstream basin (on the left) to the downstream basin, we will use the Muskingum routing method. 1. While still in the Edit HEC-1 Parameters dialog, click the <- Previous Hydrograph Station button to select Outlet 4C 2. Click the Routing Data button 3. Choose the Muskingum (RM) option 4. Click the Compute NSTPS button 5. Choose the From Channel Velocity Estimate option 6. Enter 4 for the velocity estimate 7. Select OK two times to return to the main HEC-1 dialog 8. Select Done to close the HEC-1 dialog 1.5 Save and Run the HEC-1 Simulation 1. Select HEC-1 Run Simulation 2. Click the browse button next to the Input File 3. For the file name enter Maricopa and click Save (this specifies the file name but does not actually save it) 4. Verify that the Save file before run is toggled on 5. Select OK 6. Select Close when the HEC-1 simulation finishes Now that HEC-1 computed basin and outlet hydrographs, we can view the hydrographs with the visualization tools in WMS. To view the computed hydrographs: 7. Click on any of the hydrograph icons 8. Select Display Open Hydrograph Plot. Alternatively, you can double-click on a hydrograph icon to view the hydrograph plot.

9. Close the hydrograph plot window Maricopa County: NFF and HEC-1 1-15

2 Maricopa County: Master Plan Creating a Predictive HEC-1 Model CHAPTER 2 Maricopa County: Master Plan Creating a Predictive HEC-1 Model 2.1 Objectives This exercise illustrates the use of a watershed model to predict possible hydrologic reactions based on planned land use developments. The following sections will show you how to use WMS to: 1. Define the watershed of interest 2. Build a Maricopa County HEC-1 simulation 3. Run HEC-1 based on existing land use and soil conditions 4. Run HEC-1 based on proposed conditions 2.2 Defining the Watershed To create the basins to be used in our HEC-1 simulations, we will use a shapefile containing pre-delineated sub basins for the Maricopa County. Also, we will manually create drainage outlets and feature stream arcs for the basins of interest. Finally, we will use WMS to compute the hydrologic parameters for our watershed basins.

2-2 WMS Maricopa County Tutorials 2.2.1 Converting the Shapefile to Feature Polygons 1. Close all instances of WMS 2. Open WMS 3. Switch to the GIS module 4. Select Data Add Shapefile Data 5. Locate the folder C:\WMS80\tutorial\Maricopa\tut2 6. Open basins.shp 7. Select File Open 8. Open zoom_here.wpr. This file identifies the basins used in this exercise. 9. Select the Zoom tool 10. Drag a box approximately around the rectangle shown in Figure 2-1 Figure 2-1: Zoom in on the area bounded by the rectangle

Maricopa County: Master Plan Creating a Predictive HEC-1 Model 2-3 We will select two basins before converting the shapefile to feature polygons (when mapping shapefile data to feature objects, only the selected shapes are converted). 11. Choose the Select Shapes tool 12. Multi-select the two polygons shown in Figure 2-2 by holding the SHIFT key while selecting each polygon Figure 2-2: Select the two polygons highlighted in yellow 13. Select Mapping Shapes -> Feature Objects 14. Select Next 15. Select Next 16. Select Finish The feature polygons have now been created and we are ready to create the stream arcs. Before continuing, we will remove the basins shapefile from the Project Explorer: 17. Right-click basins.shp in the Project Explorer and select Delete 2.2.2 Getting a Background Image Using the TerraServer To aid us in drawing the stream arcs, we will import a background map depicting some of the geographic features within the watershed.

2-4 WMS Maricopa County Tutorials 1. Select File Open 2. Open maricopa.jpg 3. Switch to the Map module 4. Select the Create Feature Arc tool 5. Select Feature Objects Attributes 6. Change the Arc type to Stream 7. Select OK 8. Using Figure 2-3 as a guide, begin drawing an arc from the location labeled Start Here. Click along the outline of the stream shown on the topo map so that the arc represents the stream s geometry. Doubleclick at the location labeled End Here to end the arc. Figure 2-3: Guide for creating the first stream arc. Double-click to end the arc 9. Draw a second stream arc as indicated in Figure 2-4

Maricopa County: Master Plan Creating a Predictive HEC-1 Model 2-5 Figure 2-4: Location of the second stream arc Having created the stream arcs, we will define their shared node as an Outlet point: 10. Select the Select Feature Point tool 11. Double-click on the node labeled Start Here in Figure 2-4 12. Change the Point type to Drainage outlet 13. Select OK 2.2.3 Compute the Basin Data You have completed the watershed construction and are ready to compute the basin parameters that will be used by HEC-1 1. Select Feature Objects Compute Basin Data 2. Click the Current Coordinates button 3. Change both the Horizontal and Vertical Units to U.S. Survey Feet 4. Select OK 5. Verify that the Parameter Units are Square miles for Basin Areas and Feet for Distances

2-6 WMS Maricopa County Tutorials 6. Select OK 2.3 Building the HEC-1 Model Having computed parameters such as basin area, slope, and length, we will proceed to set up a HEC-1 simulation. 2.3.1 Initialize Rainfall Data 1. Switch to the Hydrologic Modeling module 2. Select HEC-1 from the model drop-down box 3. Select HEC-1 Job Control 4. Click the Initialize Maricopa County Precipitation Data button 5. Choose the Basin Average method and change the duration to 6 hour 6. Click on the Browse button to select a rainfall grid to read in and use to compute precipitation 7. Open noaa50y6h 8. Select OK to close the Compute Rainfall dialog 9. Select OK twice more to return to the WMS window 2.3.2 Define Unit Hydrograph Method 1. Double-click on the left basin icon 2. Click the Unit Hydrograph Method button 3. Click the Compute Parameters-Basin Data button 4. Set the Computation type to Compute Lag Time 5. Select Tulsa Rural Method from the Method drop-down box 6. Highlight the line containing S Maximum flow distance slope from the Variable list by clicking on it 7. Enter 2000 in the Variable value field 8. Highlight the line containing the variable S once again to update its value

Maricopa County: Master Plan Creating a Predictive HEC-1 Model 2-7 9. Select OK 10. Choose the Given unit hydrograph (UI) option 11. Select the Maricopa County S-Graph button 12. Choose Phoenix Valley as the S-Graph type and select OK 13. Select OK to exit the XY Series Editor 14. Select OK to exit the Unit Hydrograph Method dialog 15. Click the Next Hydrograph Station -> button twice to edit the basin on the right 16. Repeat steps 2 thru 14 above to define the unit hydrograph for this basin. In this case, however, enter 2400 for the variable S Max flow distance slope. 2.3.3 Define Routing Method 1. Click the <- Previous Hydrograph Station button to select the outlet located between the two basins 2. Click the Routing Data button 3. Choose the Muskingum (RM) option 4. Click the Compute NSTPS button 5. Choose the From Channel Velocity Estimate option 6. Enter 6 for the velocity estimate and select OK 7. Select OK to exit the HEC-1 Routing Data dialog 8. Select Done to exit the Edit HEC-1 Parameters dialog 2.3.4 Import the Soil Type and Land Use Coverages The last parameter we need to define before running HEC-1 is the Green-Ampt losses. To have WMS compute losses, we will create one soil-type coverage and three land-use coverages (one representing existing land-use conditions and two representing future land-use scenarios). 1. Switch to the Map module 2. Choose the Select Drawing Objects tool at the bottom of screen

2-8 WMS Maricopa County Tutorials 3. Select the rectangle surrounding our two basins and press DELETE 4. Right-click on the Coverages folder in the Project Explorer and select New Coverage 5. Change the Coverage type to Soil Type (notice that the coverage name is automatically changed to Soil Type ) 6. Select OK 7. Create another new coverage and change its type to Land Use 8. Set the coverage name as LU existing 9. Select OK 10. Create two more Land Use type coverages and name them LU future 1 and LU future 2, respectively 11. Select the LU existing coverage in the Project Explorer to activate it 12. Switch to the GIS module 13. Select Data Add Shapefile Data 14. Open ExistingCondition.shp 15. Select Mapping Shapes -> Feature Objects 16. Select Yes when asked if you want to use all shapes 17. Select Next 18. Find the column labeled LDUSE_LID and change its Mapping field to Land use 19. Select Next 20. Select Finish 21. Select LU future 1 in the Project Explorer to activate it 22. Hide ExistingCondition.shp by un-checking its box in the Project Explorer 23. Switch to the GIS module 24. Select Data Add Shapefile Data

Maricopa County: Master Plan Creating a Predictive HEC-1 Model 2-9 25. Open LU_future1.shp 26. Choose the Select Shapes tool 27. Draw a selection box around the two basins (the extents of the watershed area) By drawing a selection box around the extents of our watershed area, we select all land use polygons that overlap our watershed. 28. Select Mapping Shapes -> Feature Objects 29. Select Next 30. Notice that in this case, the LU_CODE field was automatically mapped to the Land use attribute 31. Select Next 32. Select Finish 33. Activate the LU future 2 coverage in the Project Explorer 34. Hide LU_future1.shp by un-checking its box in the Project Explorer 35. Switch to the GIS module 36. Select Data Add Shapefile Data 37. Open LU_future2.shp 38. Choose the Select Shapes tool 39. Draw a selection box around the two basins (the extents of the watershed area) 40. Select Mapping Shapes -> Feature Objects 41. Consecutively select Next, Next, and Finish 42. Activate the Soil Type coverage in the Project Explorer 43. Hide LU_future2.shp by un-checking its box in the Project Explorer 44. Switch to the GIS module 45. Select Data Add Shapefile Data 46. Open soilwhitetanks.shp

2-10 WMS Maricopa County Tutorials 47. Choose the Select Shapes tool 48. Draw a selection box around the two basins (the extents of the watershed area) 49. Select Mapping Shapes -> Feature Objects 50. Select Next 51. Find the column labeled SLTYP_LID and change its Mapping field to SCS soil type 52. Select Next 53. Select Finish 54. Hide soilwhitetanks.shp by un-checking its box in the Project Explorer 2.3.5 Computing Losses 1. Switch to the Hydrologic Modeling module 2. Select Calculators Compute GIS Attributes 3. Change the Computation field to Green-Ampt parameters 4. Select the Land use mapping option at the bottom 5. Click the Import button 6. Open landusemagtable.tbl 7. Select the Soil type mapping option 8. Click the Import button 9. Select OK if you receive a warning that any previous tables will be replaced 10. Open soiltable.tbl 11. Set the land use coverage name field to LU Existing 12. Select OK We have computed the losses for the existing land use conditions. Later, when we want to compute runoff values for the future scenarios, we will simply recompute losses in the Compute GIS Attributes calculator.

Maricopa County: Master Plan Creating a Predictive HEC-1 Model 2-11 2.4 Run HEC-1 for Existing Conditions 1. Select HEC-1 Run Simulation 2. Click the browse button next to the Input File 3. For the file name enter Mp_existing and click Save (this specifies the file name but does not actually save it) 4. Verify that the Save file before run is toggled on 5. Select OK 6. Select Close when the HEC-1 simulation finishes 7. Double-click on the most downstream hydrograph icon (farthest to the right) 8. The hydrograph shows that for the existing land use conditions, the peak runoff for a 50 year, 6 hour storm is approximately 1260 cfs. 9. Close the hydrograph plot window 2.5 Run HEC-1 for the Proposed Conditions 1. Select Calculators Compute GIS Attributes 2. Change the land use coverage name to LU future 1 3. Change the Computation field to Green-Ampt parameters 4. Select OK 5. Select HEC-1 Run Simulation 6. Click the browse button next to the Input File 7. For the file name enter MP_future1 and click Save (this specifies the file name but does not actually save it) 8. Verify that the Save file before run is toggled on 9. Select OK to run HEC-1 10. Select Close when the HEC-1 simulation finishes 11. Double-click on the most downstream hydrograph icon

2-12 WMS Maricopa County Tutorials 12. In the upper left-hand corner of the Plot Window, note that the peak runoff has increased to 1440 cfs. This new hydrograph is superimposed over the previous one. We can zoom in on a portion of the hydrographs and/or maximize the Plot Window to enlarge the graph(s). 13. Drag a box around the peaks of the hydrographs 14. Right-click anywhere within the Plot window and select Maximize Plot 15. Press the ESC key to return the Plot window to its original size 16. To view the entire hydrographs once more, right-click anywhere within the Plot Window and select Frame Plot 17. Close the plot window 18. Select Calculators Compute GIS Attributes 19. Change the land use coverage name to LU future 2 20. Select OK 21. Select HEC-1 Run Simulation 22. Click the browse button next to the Input File 23. For the file name enter MP_future2 and click Save (this specifies the file name but does not actually save it) 24. Verify that the Save file before run is toggled on 25. Select OK to run HEC-1 26. Select Close when the HEC-1 simulation finishes 27. Double-click on the most downstream hydrograph icon 28. Notice that the peak runoff for LU future 2 (1460cfs) is slightly higher than for LU future 1. The results we are viewing in the plot window can be exported as tabular data. 29. Right-click within the Plot window and select Export/Print 30. Change the Export type to Text / Data Only 31. Change the Export destination to File

Maricopa County: Master Plan Creating a Predictive HEC-1 Model 2-13 32. Click the Browse button 33. Specify a path and filename 34. Click the Export button 35. Leave the options at the default settings and click the Export button The exported data can now be opened in a spreadsheet editor for further manipulation. Another effective way to view HEC-1 results is to browse the HEC-1 output file (*.out), which can be viewed with any text editor. Also, if HEC-1 had not terminated successfully, then checking the (*.out) file might reveal possible errors and/or warnings.