CEEn-531 Dr. Nelson
Overview
The same types of options for defining spatial and temporal variations of rainfall input are used for distributed models like GSSHA. The mechanics of how it is done are somewhat different, but the same general principles apply. You should remember that GSSHA wants all rainfall data in mm and not inches, so you will have to do some conversions of your data values.
For this assignment you will need to get a basic model of GSSHA going. While you can probably use one of the previously saved Judy's Branch projects, I recommend that you begin again from scratch (or at least from the basic delineated model that was suggested you save from the previous assignment).
To develop your basic GSSHA project:
Delineate the Judy's Branch watershed
Create a GSSHA grid with 90m sized grid cells.
Define a uniform index map with a roughness of .03
Eliminate all Digital Dams
Use a uniform precipitation storm (maybe 20 mm/hr for 2-3 hours) to get some water on it and know that surface runoff is working.
Define channel routing using trapezoid cross sections with the following dimensions: Bottom Width 5m a Depth of 4m with a 2 to 1 H:V side slope and Manning's n 0.027. Redistribute vertices to 100 meters. Turn on Diffusive Wave channel routing in the Job control.
After you get this model running and stable, save this as your base GSSHA modeling project. This model set up will be the starting point for many of your future assignments. (If you want to be really safe, you could create a zip file of all the files needed for this base model as a backup that you can't easily overwrite.)
Creating a GSSHA Gage Using a WMS Rain Gage Coverage
You can also create a WMS rain gage coverage that can be used to set up a GSSHA gage file. To do this you can follow these steps:
Right click on the coverages folder in WMS and create a new coverage.
Make sure this coverage is a rain gage type coverage and create as you did in the previous homework assignment.
Change the tool to select feature points and double click on the gage. Make sure that it is identified as a GSSHA gage.
Define the rainfall depths and distributions.
Go to the GSSHA Precipitation command and turn on Gage
Select the WMS rain gage coverage, or event you wish to simulate.
Save the GSSHA project
Run GSSHA
Assignment
Once you have the basic setup of your GSSHA model established you should perform the following analyses (don't forget to enter rainfall depths in mm):
Determine the storm total from the St. Louis gage for July 28-29 and run GSSHA using this depth with a user defined hyetograph and:
A uniform intensity over a 24 hr duration (probably a pretty small value)
An SCS Type II Distribution
The actual Distribution
Change the depth to the arithmetic average of the July 18 storm with the Type II distribution and run GSSHA.
Create a rain gage coverage for GSSHA that includes all four gages, using the July 18 storm totals and the Type II distribution for each with:
Thiessen interpolation
IDW interpolation
To turn in Now:
To turn in with Assignment 17 (but at least think about these now):
Hydrographs from all of the above scenarios. Download the template found here and copy and paste in your runoff hydrograph values from WMS inthe appropriate columns.
Try to think of 2-3 other comparisons or interesting model runs and generate graphs to include in your excel sheet. (For example, what do the uniform intensity results look like in HMS vs. GSSHA)
- Compare the results of the different temporal distribution patterns.
Compare the results the single gage vs multiple gages with the different interpolation methods.