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Flow Velocity and Travel Time Determination on Grid Basis Using Spatially Varied Hydraulic Radius

M. A. Gad*

Irrigation and Hydraulics Laboratory, Civil Engineering Department, Faculty of Engineering, Ain-Shams University, Cairo, Egypt 11566

*Corresponding author. Tel: +2-0100-5293387 Fax: +2-026830947 Email:


The hydraulic radius has always been a difficult variable to be estimated using the available data for ungauged flood routes, especially if grid-based calculations are used. This difficulty arises since the available digital elevation models are usually of poor resolution to describe the cross sectional details especially in arid and semiarid regions. This research develops a new grid-based technique to estimate travel time using spatially varied hydraulic radius. The technique implements the stream power formulation to relate the hydraulic radius R at any cross section to the hydrologic parameters of the upstream catchment area. A spatially varied grid-based Manning’s formula is used to determine flow velocity from the calculated hydraulic radius. Many anticipated uses of the developed technique are expected.

Keywords: grid, velocity, hydraulic radius, rainfall, runoff, modeling, watershed, GIS

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