You will be performing a watershed analysis of the South Fork of the Provo River.  This is the watershed to the south and east of the highway about half way up Provo Canyon as shown in the maps below (the first is to give you a general idea of the area, but you will need the Data covering approximately the area shown in the second).  You will develop a report (word document) that answers the questions below as indicated by the Red text.  I want you to print this document at the end of the exam (but saving often is recommended).  Please keep the original document in case there are any questions later.  Be sure to make your report easy to read, concise and as professional as possible.  You are on your honor to NOT collaborate or seek information from any other person in or out of the class.  Good Luck!

Figure 1: Rough map of the watershed location

1.      Download your DEM data from the USGS National Elevation Dataset (you can start from http://emrl.byu.edu/gsda).  If you pick an area larger than 10 MB you have too much area and should try to zoom in on the watershed a little more).  The server can have difficulties from time to time so start this early, and if you simply get bogged down, you can download my file.

2.     Download both the topographic map(s) and aerial photograph(s) from the teraserver that can be used to help you identify your watershed area.  You do not need to have one with a high resolution and lots of detail, but I do expect that your image(s) cover the extent of the watershed for full credit.

3.     Download the land use and soils files necessary to compute a composite CN value.  I’ve helped you out with these a little since we have not had a lot of time to investigate downloading land use and soils information.  These were downloaded from the EPA site, clipped out, transformed to UTM NAD27, zone 12 coordinates, and then saved as shape files.  Also, the hydrologic soil group field has already been joined and saved to the soil attribute table.

4.     (9 pts) Load each of these four datasets (DEM, image, soils, land use) and delineate the watershed using the DEM method.  Make the outlet point just upstream of the junction with the Provo River (the Provo River parallels the highway up Provo Canyon and will be visible form your map).  Save a picture of your delineated watershed with the topographic map in the background, color-filled contours with appropriate transparency, and the drainage area (sq. miles) visible.  Save a second picture of your watershed that has the contours turned off and the aerial photo rather than the topographic map in the background.  At this point I recommend saving your project.

5.      (2 pts) Use the land use and soils shape files to compute a composite CN value for the watershed.  Use this table after extracting from the self extracting .exe file to map the CN values for each of the land uses. What is the composite CN?  Include a picture that shows the CN labeled.

6.      (5 pts) Run an HEC-HMS model for the watershed as a single basin defined by the following information:

·        Use the computed SCS CN value that should already be defined when you specify this method.  Compute the Initial Abstraction as: Ia = 0.2*S where S is defined from the CN: S = (1000/CN)-10.  Enter Ia appropriately. 

·        Use the Clark Unit Hydrograph method for transformation with the ADOT Method (Desert/Mountain) to calculate the time of concentration (include the computed value of Tc in your report).

·        Use an SCS Hypothetical Storm with a Type II distribution and a depth of 3.2 inches for the meteorological model. 

·        Use a computational time interval of 15 minutes.

·        The duration of the simulation should be 36 hours.

Run HEC-HMS include the hydrograph in your report as well as explicitly stating the time of concentration, peak flow (CFS) and volume (inches).

7.      (5 pts) Now add a second interior outlet at approximately 456291, 4464290 (see the map above).  Place it in such a way as to create only a single basin upstream.

·        Determine and record in your report the composite CN for both the sub basins.  Include a picture of your delineated watershed with sub basins with the display of area and CN.

·        Create a second HEC-HMS simulation that routes the flow from the upstream basin using the Muskingum method. 

·        Use the same storm of 3.2 inches for both basins.

·        Use the SCS loss rate method, compute Ia for each of the sub basins as before.

·        Use the Clark Unit Hydrograph method for transformation with the ADOT Method (Desert/Mountain) to compute the time of concentration for both sub basins.

·        Use the following Muskingum parameters to route the upstream hydrograph through the channel:

o       Muskingus K = 2.5 hr

o       Muskingus X = 0.25

o       Number of sub reaches 10

·        Simulate 36 hrs of duration with a 15 minute time interval.

·        Run HEC-HMS include the hydrograph in your report as well as explicitly stating the peak flow (CFS) and volume (inches) at the outlet. Would you say this channel has a relatively high or low attenuation and lag, why?

8.      (5 pts) Now create a new instance of the watershed and set up a MODClark model.

·        Create 100 by 100 MODClark grid cells.

·        Use the same SCS storm, except that for MODClark you will need to define this in the Meteorological Model as a User Hyetograph instead of an SCS Hypothetical Storm.  You will need this file to import the SCS Type II XY Series data.  Use 3.2 inches for the rainfall depth.

·        Compute the grid CN parameters.

·        Set the initial abstraction ratio to be 0.2 (this will calculate Ia=0.2S internally), and potential retention factor to be 1.0.

·        Use the MODClark transform method and use the ADOT Method (Desert/Mountain) to determine the time of concentration.

·        Simulate 36 hrs of duration with a 15 minute time interval.

·        Run HEC-HMS include the hydrograph in your report as well as explicitly stating the peak flow (CFS) and volume (inches) at the outlet.

9.      (8 pts) Plot the resulting hydrographs from the 3 analyses in a single plot using excel.  Use a legend to clearly identify each and include in your report.  Then, briefly discuss the results between the single basin analysis, multi-basin with routing analysis, and MODClark quasi-distributed analysis.  Note differences in peak flow, volumes, and hydrograph shape and explain why you believe there are (or are not) differences?

10.  (6 pts) Finally create a GSSHA model with a grid cell size of 90 m for the same watershed and define the following values (see hints at end)

1.      In the Job Control set the following:

1.      Total time = 1000 min

2.      Time step =5 sec

3.      Outlet Slope 0.01 m/m

4.      Go into Output Control and set the output to be in English so you can compare the results in cfs to the previous models (though these models are not intended to be exactly comparable).

2.      Use the land use data to prepare index map. (You are not using uniform index rather your index map will have different indices depending upon your land use data). You will use this index map for roughness table. You can use the following roughness values of LUCODE (32 - 0.022, 41 -0.020, 42 – 0.027, 43 – 0.031)  Show a picture of the grid with the mapped indices. See note 2 below about not having the index map highlighted when saving the GSSHA Project.

3.      Fix the digital dams using cleandam.exe program. Enter a uniform precipitation of 10.16 mm/hr over a period of 8 hrs (i.e. 480 min).  Note this is equivalent to 3.2 inches though for GSSHA we are letting it occur in 8 hours instead of the 24 that we used in HMS.

4.      Successfully Run GSSHA.  Cleandam will eliminate all digital dams so you should see most of the flow accumulate in the channel grid cells and will develop a hydrograph at the outlet in the .otl file.

5.      Show a picture of the surface depths for a time step where there is significant depth in the channel grid cells. Examine the summary file and note volumes of rain, discharge, and remaining on the surface.  Plot your outlet hydrograph (found in the .otl file) with the results from the HMS simulations and comment on the peak, volume, shape, etc. as compared to HMS.  It will not look the same so don’t expect that it should, but comment on what you believe causes the differences.

Hints for WMS/GSSHA.

There a few bugs we have discovered in the WMS-GSSHA interface that I want you to be aware of.  Despite these problems I would expect that within 30 minutes you can easily finish this run.  If you find you have spent more than 2 hours and don’t have GSSHA running STOP.  Notice it is only worth 6 points so turn in what you have and move on.  Here are a few hints to work around some known problems.

1.      Save your WMS project with the delineated basin before you get started.

2.      After you create your index map you will want to select the dataset so you can see that they are mapped.  This is good, but if you save the GSSHA project with this index mapped selected WMS will crash.  So, be sure to select the elevation dataset before saving the GSSHA project.

3.      I have also had an error from time to time when running GSSHA that says something like “the uniform roughness is 0.00” and this stops GSSHA from running.  I get this message even though I have defined an index map.  If you have this problem I would suggest resaving the GSSHA project in a different directory by a different name.

4.      Always save GSSHA projects in directories without spaces (no My Documents, or Desktop) like, “C:\GSSHAProjects” or something.  It will work in other places sometimes, but I have noticed that it has problems with either spaces or long names some times so avoid that kind of naming if possible.