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This page contains an archive of the web seminar given in May 2009. To view this archive, you will first need to download and install the windows player from AT&T and WebEx]. This player can be downloaded here. After you download and install the player, download the recording, start the player and open the recording in the player program (Select File | Open from the menu and then open the Webinar ending in ".wrf").

  • Download and install the player directly from here.
  • Download the web seminar here (24.3 MB).
  • You can also download the web seminar as a windows media file here (139.6 MB, you will not need to install the player if you download this version, but it is much larger).

Webinar Questions and Answers

How are antecedent conditions set for each run?

You can enter in the initial soil moisture using an index map basing it on soil type, land use, or both. When running in continuous simulation mode, the model calculates the antecedent moisture conditions.

What type of grid structure do you use for groundwater flow?

The model uses the same grid that is used for overland flow.

Is it possible to import pre-delineated watersheds into WMS?

Yes. You can read in a pre-delineated watershed as an ArcGIS file, such as a shapefile, as vector data, and then map it to a DEM to include the elevations in your watershed.

Does the model have the capability to work with NRCS Soil Data Mart data?

Yes. You can download NRCS data as shapefiles (vector data) or NED GridFloat (raster data).

What would you expect for a typical run-time for one million grid elements?

The duration depends on the processes that you are simulating. Simulating more processes means more run-time. One million grid elements would probably take a long time.

Is there a limitation with regards to the size of the watershed one can run?

You can run watersheds of all sizes.

Is it possible to use actual ET derived from remote sensing as input?

Currently, the ET is calculated in the model.

Can GSSHA use LIDAR data to define basin elevations?

Yes. To use LIDAR data, you would read it into WMS and create the grid from that data. However, some of the advantages of LIDAR data may be lost due to the grid cell size being larger than the LIDAR data size.

You mentioned the Green-Ampt infiltration calculation. What other ways of calculating runoff generation does GSSHA support?

You can simulate using a standard Green-Ampt model, Green-Ampt with redistribution, Green-Ampt using multiple layers, and an unsaturated groundwater flow using Richard's Equation.

Is it possible to analyze hydraulics of a storm sewer line?

There is a storm sewer and tile drain model in beta mode right now, but this is not in the release version yet.

Can you simulate the hydrologic model on a closed-system, without rivers, for example on isolated wetlands?

Yes. You can run just overland and groundwater flow.

How was rainfall introduced?

A constant or uniform rainfall of 1 inch per hour over two hours was used in this simulation.

What kind of file format is needed for radar-based rainfall?

The National Weather Service has a tool to convert the radar data to an ArcInfo ASCII grid. This data can then be read into WMS, which will convert it to the correct format for GSSHA.

How does the model handle uncertainty? Is it possible to input parameters as ranges and get a range of corresponding output?

GSSHA has an auto-calibration method which uses shuffled complex evolution method. GSSHA also has a stochastic mode, which can be used to enter a range of parameters.

Can you develop erosion and sediment faces along wadi banks?

Yes. You can model sediment movement in all parts of a watershed.

Can the flows generated in GSSHA be used with HEC software?

Yes, you can feed them in as hydrographs.

What type of DEM is necessary for watershed scale simulation? Will USGS data provide accurate results, or is higher resolution data required

This depends on the needs of your model, but for the standard model, USGS data is sufficient. However, if you were modeling a flat area, you may need survey data.

What research is occurring regarding parallel processing, GPUs, and code efficiency?

A version of GSSHA that utilizes parallel processes is currently being worked on.

Would output from GMS be valid as input for GSSHA?

You can use the water table dataset from GMS as input for GSSHA.