Description of WMS Watershed Modeling System

What Model Does Integrates GIS and hydrologic models Uses digital terrain data to define watershed and sub basin characteristics Provides interface for hydrologic models widely used in industry Provides useful calculators for hydrologists and engineers

Digital Terrain Models Input Three primary sources for model development Geographic Information Systems (GIS) Data Digital Elevation Models (DEMs) Triangulated Irregular Networks (TINs)

Digital Terrain Models: DEM

Digital Terrain Models: TIN

Digital Terrain Models: GIS Data

Digital Terrain Models Output: Delineates basin boundaries Tool for obtaining basin characteristics such as: Land Use Lag Times Time Area Curves Curve Numbers Areas Slopes Runoff Distances

Digital Terrain Model: Uses Land Use and Soil Type

Digital Terrain Model: Uses Composite Curve Number

Digital Terrain Model: Uses Time of Concentration

Calculators: Detention Basins Detention Basin Analysis/Design EAV Curves form a TIN Route hydrographs through basin

Calculators: Channels “Cut” cross sections from DEM or TIN Examine hydraulic properties Export for use in other applications (i.e. RAS)

Calculators: Channels Delineate Flood Plain

Calculators: Channels Hydraulic calculations

Calculators: Culverts HY8 culvert analysis program included in WMS

Calculators: Curb and Gutter Flow The FHWA HEC22 equations are built into WMS and can be used to examine flow across storm drain inlets for a variety of curb and gutter openings.

Hydrologic Models Provides graphical interfaces and actual following models : HEC-1 HSPF TR-20 and TR-55 Rational Method NFF

Hydrologic Models: HEC-1 Description Flood hydrograph program that models the rainfall-runoff process Input: Basin model Many characteristics obtained from digital terrain model Precipitation model Control specifications Output Hydrographs at any hydrologic feature

Hydrologic Models: HSPF Description: Model developed by the USGS Simulates hydrologic and water quality processes on land surfaces, streams and impoundments Generally used to assess the effects of land-use change, reservoir operations, point or nonpoint source treatment alternatives, flow diversions, etc.

Hydrologic Models: HSPF Input: Time history of rainfall, temperature and solar radiation, land use characteristics Output: Time history of the quantity and quality of runoff from an urban or agricultural watershed. Flow rates, sediment loads, nutrient and pesticide concentrations

Hydrologic Models: TR-55, TR-20 Description: TR-55 and TR-20 both model the rainfall runoff process with TR-55 being used especially for small, urban or urbanizing watersheds. Input: Land characteristics to calculate curve numbers Rainfall model Basin model Output: Hydrographs

Hydrologic Models: Rational Method Q = CiA (I’m assuming we are all familiar with this) WMS provides a rational method calculator Generates IDF curves for eastern US FHA Kinematic wave equation can estimate Tc of basin given: Manning’s n, basin length, slope Output is peak flow of basin

Hydrologic Models: NFF Description: Developed by FEMA, FHA, and USGS Uses regression equations to estimate T- year flood-peak discharges for rural and urban watersheds Most of the equations are a function of basin area, stream length, and other parameters easily computed from digital terrain models.

Hydrologic Models: NFF Input: Basin characteristics Basin location (State and region) Output Peak flood flows for basin Typical flood hydrographs for given T-year peak discharge

More on WMS Contains Hydrology for LA County and Maricopa County Hydrographs and other data produced in WMS can be exported for use in standard spreadsheet software Free extension to Arcview GIS program “WMS Hydro” This extension can be used to prepare land use, soil, or elevation data for use by WMS and it can also be used to manage/view results produced by WMS.

Summary Powerful Model Integrates GIS technology with hydrologic models Useful calculators According to Ryan, fairly easy to use