Modeling Project Part 1

Basic Model Formulation

Dr. Nelson


This assignment will help you review the different models and modeling options studied this semester.  It will also help us determine how well the HMS and GSSHA models can be applied to solve the runoff for a watershed for an actual event.  It is to be done individually in order to insure that you are all prepared for the final, but it is okay to

You will be provided with the data necessary to develop a model and after you run the simulation we will compare it to observed runoff.  After that we will calibrate the model and later on validate it by simulating another storm.

The watershed you will be using is in Wisconsin and part of the Eau Galle basin named 8 Mile Creek.  You will  perform the analysis with Green and Ampt infiltration for both HMS and GSSHA.


Get the following data and perform the tasks listed

DEM data         Soil Type data            Land use data

 Explore and understand the data thoroughly before you proceed to modeling.


This is a small watershed compared to what you have been working with before (less than a square mile) and unless you lower the flow accumulation threshold you will not generate stream arcs when you run TOPAZ. So, in the display options under DEM data change the Minimum Accumulation for Display to a smaller number than the default of 1 sq. mile. Your basin should look somewhat like this (note the approximate location of the outlet).

Delineate the watershed, get the land use and soil type coverages mapped based on the GIS data provided and save it as the Base WMS project. This will be the starting point for further modeling with HMS and GSSHA.

HMS set up

Your final HMS model should have single Green and Ampt infiltration model (lumped) that we will define an actual storm (will be provided) for the meteorological model. Use the Clark Method for the transformation. Ultimately you will use this model and optimize (estimate parameters from observed data) for both the Clark and G&A parameters based on peak and volume optimization. For optimization, you will be provided with the observed data set for the real storm and you will compare the outcomes of your model with the real storm.

The following guidelines should be helpful to you 

GSSHA set up

Your final GSSHA model should have 30m grid, Green and Ampt with redistribution infiltration model with a real storm (will be provided). You will have variable roughness and variable infiltration parameters based on land use and soil type data.  You will want to create an index map based on both the land use and soil coverages because this is probably more realistic for defining infiltration. Your model should have rivers turned on, redistributed and smoothened.

You already have a lot of experience on GSSHA modeling but it is good to always follow the following sequence of processes for better modeling performance.  

Useful links and references:

GSSHA reference Manual - Table 10, page 94

Manning's n values are available here and here.

Do not hesitate to refer to previous assignments.

PS: This is an initial model, we are mostly interested in your "best" effort at getting a result.  Don't worry if it is different than another person, what we want is the solution from your best modeling practice. You will see how close to reality you have modeled your watershed later, and it is a good time to judge your/our modeling skills developed throughout this semester. Do not hesitate to ask me or the TA for help.

Using the Real Storm Data

Before your begin this part, you must have your basic HMS (G&A) and GSSHA models running with the specifications described above.

You will now use an actual storm (attached below in this page) and see how your HMS and GSSHA models respond to this storm event. The precipitation data provided here has 15 minutes interval incremental data for a duration of  approximately 14 hours and are in mm. Be careful about the units as GSSHA requires metric and you can use both the units in HMS (but use English units for this project). 

To define the rainfall data in HMS, you have to select the user hyetograph option and copy and paste the data into the XY series editor of WMS. DO NOT forget to turn on the Incremental Data below the XY series editor. After you have entered the values, you will have to define the rainfall depth in the Meteorological model editor, enter the depth to be 2.36 in.. You do not need dates for HMS so just enter time interval in an increment of 15 minutes.

Similarly, to define the rainfall for GSSHA, you have create a Rain gage coverage, create a gage  and enter the gage data. There will be single gage and be careful, in GSSHA you need to define the dates of each increment.

After you run both HMS and GSSHA models summarize the results in the template attached below and email the TA. He will then provide you with the observed flow data for the storm you are simulating. We will use this data in our report to the Corps of Engineers on how well you can use each model to simulate the results. 

This is your first shot model and do not worry about getting the model match the observed flow for now. But you still need to make sure that your are getting reasonable results. In the next part of this project, you will compare your results with observed data and do optimization/calibration, but for now we want your best answer.

Get the Storm Data here. You can see the recent precipitation in this basin here.

Get a Template for summarizing your results here

Submit your simulated results on learning suite.