Difference between revisions of "Module Runoff"
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==Main Processes== | ==Main Processes== | ||
The runoff is calculated by the Manning's equation as follow: | The runoff is calculated by the Manning's equation as follow: | ||
| + | Q=\frac{1}{n}\cdot A\cdot R_{h}^{2/3}\cdot s^{1/2} | ||
| + | where: | ||
| + | :{| | ||
| + | |- | ||
| + | | ''V'' || is the cross-sectional average velocity (ft/s, m/s) | ||
| + | |- | ||
| + | | ''k'' || is a conversion constant equal to 1.486 for [[U.S. customary units]] or 1.0 for [[SI units]] | ||
| + | |- | ||
| + | | ''n'' || is the '''Gauckler–Manning coefficient''' (independent of units) | ||
| + | |- | ||
| + | | ''R''<sub>''h''</sub> {{pad|0.5em}}|| is the hydraulic radius (ft, m) | ||
| + | |- | ||
| + | | ''S'' || is the slope of the water surface or the linear [[hydraulic head]] loss (ft/ft, m/m) (''S'' = ''h''<sub>''f''</sub>/''L'') | ||
| + | |} | ||
==Other Features== | ==Other Features== | ||
Revision as of 16:08, 18 February 2011
Contents
Overview
Module Runoff allows the calculation of the overland surface runoff over a regular structured grid as function of precipitation, infiltration and terrain slope. In particular the runoff is evaluated by the Manning’s equation.
Main Processes
The runoff is calculated by the Manning's equation as follow: Q=\frac{1}{n}\cdot A\cdot R_{h}^{2/3}\cdot s^{1/2} where:
V is the cross-sectional average velocity (ft/s, m/s) k is a conversion constant equal to 1.486 for U.S. customary units or 1.0 for SI units n is the Gauckler–Manning coefficient (independent of units) Rh Template:Pad is the hydraulic radius (ft, m) S is the slope of the water surface or the linear hydraulic head loss (ft/ft, m/m) (S = hf/L)
Other Features
How To Generate Manning Coefficients
Manning coefficients must be provided in runoff data file.
Options:
- Use a constant value
- Define a Manning's grid: One possible option is to associate Manning with land use classes (shape file). In this case can use MOHID GIS going to menu [Tools]->[Shape to Grid Data] and provide: i) the grid (model grid), ii) the land use shape file and iii) the corespondence between land use codes and Manning.
Use Manning inicialization with Module FillMatrix standards in the block:
<BeginOverLandCoefficient> FILE_IN_TIME : NONE INITIALIZATION_METHOD : ASCII_FILE REMAIN_CONSTANT : 1 DEFAULTVALUE : 0.08 FILENAME : ..\..\GeneralData\Runoff\Mannings200m_v2.dat <EndOverLandCoefficient>
