WMS Overview

WMS (Watershed Modeling System) is a comprehensive hydrologic modeling environment for watershed analysis using HEC-1, HEC-HMS, TR20,TR55, Rational Method, and others. WMS provides tools for automated watershed and sub-basin delineation, WMS Modeling automated curve number generation, and time of concentration computation.

WMS Features

» Overview

Unmatched Modeling Capability

WMS is easy to learn and use. WMS provides complete support of the industry-standard U.S. Army Corps of Engineers HEC-1 and HEC-HMS, U.S. Soil Conservation Service TR-20 and TR-55, and Rational Method Equation hydrologic routing programs. Also supported is the recently released state-of-the-art National Flood Frequency (NFF) model, which was developed by the USGS in cooperation with the Federal Highway Administration (FHWA) and the Federal Emergency Management Agency (FEMA). In addition, support for the EPA/USGS hydrologic water quality HSPF model is also provided.

WMS provides a complete graphical interface for HEC-1, HEC-HMS, TR-20, TR-55, Rational Method, and other hydrologic routing models

HEC-1 and HEC-HMS Interface Module

The HEC-1 and HEC-HMS Interface Modules provide a complete graphical interface to the U.S. Army Corps of Engineers HEC-1 and HEC-HMS hydrologic analysis models. All modeling parameters and input data are entered through interactive graphics and easy-to-use dialog boxes, enabling the user to easily define the hydrologic routing models. There is no longer any need to struggle with cumbersome, cryptic, error-prone input card files. However, if desired, the corresponding input card file can be viewed and directly edited through a synchronized card file text editor.

Additional technical information is available for HEC-1 and HEC-HMS.

WMS will automatically generate a HEC-1, HEC-HMS, TR20, TR55, or Rational Method model, and then compute the resulting runoff hydrograph

TR-20 Module

The TR-20 Interface Module provides a complete graphical interface to the U.S. Soil Conservation Service TR-20 hydrologic analysis model. All modeling parameters and input data are entered through interactive graphics and easy-to-use dialog boxes, enabling the user to easily define the TR-20 hydrologic routing model. There is no longer any need to struggle with cumbersome, cryptic, error-prone input card files. While there are some limitations in defining computation sequences, WMS supports all TR-20 components including RUNOFF, REACH, RESVOR, and DIVERT options. If desired, the corresponding input card file can be viewed and directly edited through a synchronized card file text editor.

TR-55 Module

The TR-55 Interface Module provides a complete graphical interface to the U.S. Soil Conservation Service TR-55 hydrologic analysis model. All modeling parameters and input data are entered through interactive graphics and easy-to-use dialog boxes, enabling the user to easily define the TR-55 hydrologic routing model. TR-55 is perhaps the most widely used approach to hydrology in the United States. TR-55 provides a number of techniques that are useful for modeling small watersheds. TR-55 utilizes the SCS runoff equation to predict the peak rate of runoff as well as the total volume. TR-55 also provides a simplified "tabular method" for the generation of complete runoff hydrographs. The tabular method is a simplified technique based on calculations performed with TR-20. Additional technical information is available for TR-55.

Rational Method Interface Module

The Rational Method Interface Module provides a complete graphical interface to the industry-standard Rational Method hydrologic analysis model customarily applied to urban hydrology. WMS includes the capability to generate Intensity-Duration-Frequency (IDF) curves from HYDRO-35 maps (for the eastern U.S.), NOAA Atlas 2 Volumes I-XI maps (for the western U.S.), or user-supplied intensity data. The IDF curves can be graphically printed out or pasted into a word processor. In addition, the Kinematic Wave Equation, as defined by the Federal Highway Administration Design Handbook, can be used to compute an estimated time of concentration based upon the catchment length, slope, and Manning's roughness coefficient. Additional technical information is available for Rational Method.

HSPF Module

HSPF (Hydrologic Simulation Program - Fortran) is a watershed simulation model designed to simulate all the water quantity and water quality processes that occur in a watershed. Although it is usually classified as a lumped model, it can reproduce spatial variability by dividing the basin in hydrologically homogeneous land segments and simulating runoff for each land segment independently, using different meteorologic input data and watershed parameters. HSPF is the only model available that can simulate the continuous, dynamic event or the steady-state behavior of both hydrologic/hydraulic and water quality processes in a watershed. The model is unusual in its ability to represent the hydrologic regimes of a wide variety of streams and rivers with reasonable accuracy. Thus, the potential applications and uses of the model are comparatively large and include: flood mapping, urban drainage studies, river basin planning, studies of sedimentation and water erosion problems and in-stream water quality planning.

NFF Interface Module

The National Flood Frequency (NFF) Interface Module provides a graphical interface to the state-of-the-art USGS NFF hydrologic analysis model. This model evaluates regression equations for estimating T-year flood peak discharges for rural and urban watersheds. As many as 7 multiple regression equations (2-, 5-, 10-, 25-, 50-, 100-, and 500-year) are defined for each of the more than 200 flood regions across the United States. Additional methods are provided for estimating a typical flood hydrograph corresponding to any given T-year peak discharge. WMS contains a state-by-state and flood regional lookup database that automatically selects the appropriate regression coefficients, standard errors, and other related information for the nearly 1,500 multiple regression equations provided. When used with the DTM Module, all basin geometric parameters, such as area, slope, elevation, and basin length, are automatically computed and inserted into the selected regression equations. The user can override any of these values prior to performing the computations

DTM Module

Using the DTM (Digital Terrain Modeling) Module, WMS will build a digital terrain model of the watershed from a variety of sources. This data can be obtained from existing computer data (such as an existing digital terrain model), by importing or digitizing a contour map, downloading field survey data, importing USGS DEM (Digital Elevation Model) Maps, or importing ESRI ArcInfo® GIS (Geographical Information System) Gridded Data. If the user already has a DTM created in AutoCAD® or MicroStation®, he can directly import this TIN model as a DXF file. Otherwise, raw XYZ data points can be triangulated using the Delauney triangulation technique to create a TIN (triangulated irregular network) digital terrain model. To further aid the engineer during modeling of the watershed, TIN elements, stream channel networks, sub-basin ridge edges, spot elevations, and elevation contour lines or color-shaded elevation contours can also be displayed.

WMS will automatically subdivide a large watershed into a series of sub-basins, precisely delineate the sub-basin boundaries, compute the resulting stream channel network, determine the required hydrologic properties, and construct the corresponding hydrology model input data file—all in just a few minutes. Previously, performing this work manually required countless hours spent examining topographical maps to infer a watershed's sub-basin boundaries and to estimate each sub-basin's hydrologic properties. If digital terrain data is not available, WMS will construct an equivalent graphical stick routing model (sometimes called a sub-basin topological tree). The user can either create this model interactively, or automatically by importing an existing HEC-1, HEC-HMS, or TR-20 input data file. If required, WMS can link a pre-existing HEC-1, HEC-HMS, or TR-20 model back to a digital terrain model.

WMS can display the digital terrain model and runoff modeling results in a variety of graphical plots to aid in understanding the drainage characteristics of the watershed. Any of these plots can be combined with a contour line plot or color-shaded contour plot of the watershed, thereby enabling the engineer to easily observe corresponding elevations in the watershed model. Overland flow paths and stream channel flow paths are shown in different colors, providing a map of the flow patterns for the watershed. In addition, any of the computed hydrologic properties can be superimposed upon the displayed digital terrain model.

Map Module

Using the Map Module, scanned TIFF images of topographical maps, such as USGS quadrangle space maps, can be displayed as a background image, used for on-screen digitizing, or simply to enhance the modeling results output. Images can be registered, so that image pixel coordinates correspond exactly to real world survey coordinates.

The Map Module can also directly import and export DXF files. For example, a DXF file of streets and buildings can be overlaid on the computed floodway delineation map to show which streets and buildings will be susceptible to flood damage for a particular storm event. If desired, the user can annotate the drawing, creating text labels, lines, rectangles, and other entities on the drawing to further enhance the modeling results output. In addition, land use, soil type, and other data coverage types can be directly imported from an ESRI ArcInfo® or ArcView GIS.

Automated Hydrologic Modeling Capability

Once a TIN has been constructed, drainage characteristics can be modeled using a variety of methods. For example, flow paths can be determined in an interactive manner by using a mouse to select any point on the watershed model. The software will then trace the resulting downstream flow path from that point. Also, the software can automatically initiate a flow path from the centroid of each TIN element contained in the watershed, thereby displaying the drainage flow patterns for the entire watershed. Overland flow and stream channel flow are distinguished from one another by color.

Small depressions on the interior of the watershed can be identified. The user can then define the flow path through the depression to its spill-point. Using these spill-points and automatically identified terminus locations (where stream channel flow exits the watershed), the stream channel networks are computed and the sub-basin boundaries accurately delineated. The engineer may then add or delete stream channel definition points to further subdivide or combine sub-basins.

Once the sub-basins have been delineated, WMS will automatically compute the sub-basin properties, such as sub-basin areas, sub-basin average slope, sub-basin maximum overland flow distance, distance from the sub-basin centroid to the nearest stream, stream lengths, stream slopes, and rain gage weights using the Thiessen polygon method. Composite curve numbers and time of concentrations (or lag times) can be computed automatically using assigned land use and soil type coverages. When performing a snow melt analysis, the software can automatically compute areas within elevation zones for each basin. The user finishes defining the hydrologic model by specifying the required routing parameters through easy-to-use interactive dialog boxes.

Advanced Graphics Compatibility

After performing the hydrologic analysis, WMS will display the computed hydrographs on the digital terrain model. Hydrograph plots from different locations and different storm events can be superimposed upon each other, thereby showing routing time lag and differences between storms. If flood stage data is available, WMS will automatically delineate the floodplain on the digital terrain model. These stage values can be entered interactively or imported from an external file. Contours of flow depth can also be displayed. The resulting floodplain delineation map can then be printed, or exported to AutoCAD or MicroStation.