WMS:Assigning an Equation

HEC-1 Basin Time Computation dialog

The Basin Time Computation dialog allows selecting from one of several pre-defined equations. The Equation drop-down box lists the available methods for computing lag time or time concentration and is controlled by setting the computation type combo box to the desired setting. Once an equation has been selected, the Instructions / Results window will identify any variables with zero values and instruct to define values for them. Variables are assigned values by selecting the variable from the Variables text window and then assigning a value to it in the edit box to the right. Once all variables are defined the Instructions / Results window will display the computed lag time or time of concentration.

Basin Time Computation Dialog

Accessed by selecting Compute Parameters-Basin Data in the HEC-1 Unit Hydrograph Methods dialog. Basin – Instructions / Results (You may have to scroll down) – Computational type: –

"Compute Lag Time"

	Selections	Selection Options
	Method:	"Denver Method" "Tulsa Rural Method" – "Tulsa 50% Urban Method" – "Tulsa 100% Urban Method" – "Espey Rural Method" "Espey No Urbanization Method" "Espey Partly Urban Method" "Espey Completely Urban Method" "Riverside Mountains Method" "Riverside Foothills Method" "Eagleson Method" "USGS Nationwide Urban Method" "Putnam Method" "Taylor Method" "Colorado State University (CSU) Method" "Scs Method" "Custom Method"
	User Defined... –	Select to bring up Modify Equation dialog.
	Modify Equation...	Select to bring up the Modify Equation dialog that allows you to modify the equation used for the Basin time computation.
	Basin Variables... –	Select to open the Basin Geometric Attributes dialog.

"Compute Time of Concentration"

	Selections	Selection Options
	Method:	"User Defined Method" "Kirpich Method for overland flow on bare earth" "Kirpich Method for overland flow on grassy earth" "Kirpich Method for overland flow on asphalt" "Kirpich Method for overland flow on bare earth (Mountains)" "Kirpich Method for overland flow on grassy earth (Mountains)" "Kirpich Method for overland flow on asphalt (Mountains)" "Ramser Method for channel flow" "Fort Bend County Method" "Kerby Method for overland flow" "ADOT Method (Desert/Mountain)" "ADOT Method (Urban)"
	User Defined... –	Select to bring up Modify Equation dialog.
	Modify Equation...	Select to bring up the Modify Equation dialog that allows you to modify the equation used for the Basin time computation.
	Basin Variables... –	Select to open the Basin Geometric Attributes dialog.

• Instructions – Place that allows the reading of warnings that may occur in the equation as well as a list of pre-defined variables that are computed by WMS.

Equation – The equation being used for calculation.

• Parse – Click to parse through the equation.

Variable Abbreviations – A list of variable abbreviations relating to the equation. Definitions – A list of definitions for the variable abbreviations. Units – ||The units that apply to the definition chosen.

• "none"
• "ft"
• "m"
• "km"
• "mi"
• hr"
• "min"
• "sec"
• "sq. mi"
• "sq. km"
• "sq. ft"
• "acre"
• "hect"
• "in"
• "mm"
• "ft/mi"
• "fract"

Method:

WMS:Basin Geometric Attributes Dialog

HEC-1 Basin Geometric Attributes dialog

Accessed by selecting Basin Geometrical Attributes located in the HEC-1 Unit Hydrograph Methods dialog. Variable Names – Below the Variable Names heading is a table that allows the inputting of values for each one of the listed variables' names.

Recompute Basin Data – Select to bring up the Units dialog.

Restore Original Values – Select to revert all values in the Variable Names table back to their original values.

Related Topics

• Overview of Basin Data Equations
• Travel Times from Basin Data
• [[