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| Time of concentration should be in hours for the unit hydrograph. Several different equations exist for determining the time of concentration. Two different methods exist for computing the time of concentration using [[WMS:Travel Times from Basin Data|computed basin data]] or using [[WMS:Travel Times from Map Data|map data]]. The list of basin geometric attributes computed automatically when basins have been delineated from a TIN can be useful in many of these equations. These attributes can be viewed and edited from within the ''TR20 Basin data'' dialog by choosing the '''Basin Geometrical Attributes''' button.
| | #redirect [[WMS:TR-20 Basin Data#Time of Concentration]] |
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| ==Basin Geometric Attributes==
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| When drainage data are computed, select this button to view and edit the geometric attributes of a basin, including the basin area, the flow length, and the basin slope. The different basin attributes can be viewed and edited only after computing the basin data. The basin data may be computed by selecting the '''Compute Basin Data''' command in the '''TIN''' or '''DEM''' Drainage module menus, or in the '''Feature Objects''' map module menu.
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| ==[[WMS:Travel Times from Basin Data|Compute TC – Basin Data]]==
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| Pressing this button will bring up the ''Unit hydrograph parameter computation'' dialog. In this dialog, define the type of computation method to use in computing the time of concentration for TR20. After exiting this dialog, the time of concentration, lag time, time to peak, and Snyder coefficient will be calculated. Many of these coefficients and times can be used in HEC-1 models, and the time of concentration can be used in TR20 watershed models. By de-selecting the Do not auto-recompute parameters option, unit hydrograph parameters will be automatically re-calculated when the basin area is re-computed or other basin parameters are changed.
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| ==[[WMS:Travel Times from Map Data|Compute TC – Map Data]]==
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| Times of concentration may also be computed using a time computation coverage. The ''basin time of concentration'' dialog is accessed by selecting the [[WMS:Travel Times from Map Data|Compute TC – Map Data]] button.
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| ==Related Topics==
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| * [[WMS:TR-20|TR20 Overview]]
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| * [[WMS:TR-20 Edit Parameters|Editing TR20 Parameters]]
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| * [[WMS:TR-20 Basin Data|Entering Basin Data]]
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| {{WMSMain}}
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| [[Category:Needs Update]]
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