#114 - HEC-RAS Steady Flow (Dec 2022)

Study limit determination; defining the river system schematic; cross section geometry and locations; optional cross section properties: ineffective flow areas, levees, and blocked obstructions; defining the reach lengths between sections; energy loss coefficients; stream junction data.

This lecture will go through developing an HEC-RAS terrain model, river network, and entering and editing data tools in RAS Mapper.

Jensen

Classifications of open channel flow; velocity distribution in a channel; energy principles; cross section subdivision for conveyance calculations; friction loss equations; contraction and expansion losses; computational procedure; critical depth determination; and applications of the momentum equation

Discussions about Manning’s equation; uniform flow equations; methods for computing n values: tables, pictures, and equations; examples of calibrated n values for various streams.

Spatially varied n. End with a demo

L2.3

Viewing results; cross section plots; profile plot; X-Y-Z plot; summary tables; errors, warnings, and notes, and floodplain maps in RAS Mapper.

Nature of flow through bridges; components of bridge losses; cross-section locations; defining ineffective flow areas; contraction and expansion losses.

Available approaches to bridge loss computations within HEC-RAS; selecting the appropriate bridge modeling approach for various situations of low flow bridge hydraulics; selecting the appropriate bridge modeling approach for various situations under high flow bridge hydraulics.

Definition of terms; input requirements: cross section locations, ineffective flow areas, expansion and contraction coefficients; inlet control; outlet control; solution logic

Cross section interpolation; mixed flow regime calculations; flow distribution calculations; lateral structures and optimization; Inline Weirs and Gated Spillways. 

Calibrating a Steady Flow Model

Students will learn what data is required for model calibration and how to modify Manning’s n values to calibrate the model to observed data.

Gibson

This lecture will provide students with information on how to interpret HEC-RAS output messages (errors, warnings, and notes); diagnose common data input mistakes; and how to use the HEC-RAS Log File to understand more about the computations and possible problems

Floodway definitions; general guidelines; computer procedures; program input requirements for floodway calculations; available output.