open channel flow

[mowafi3m]

open channel flow

General
HEC-6 (HEC, 1991) is a one-dimensional movable boundary open channel flow and sediment
model designed to simulate changes in river profiles due to scour and deposition over fairly long time
periods (typically years, although applications to single flood events are possible). The continuous flow
record is broken into a sequence of steady flows of variable discharge and duration. For each flow a
water surface profile is calculated thereby providing energy slope, velocity, depth, etc. at each cross
section. Potential sediment transport rates are then computed at each section. These rates, combined
with the duration of the flow allow for a volumetric accounting of sediment for each reach. The amount of
scour or deposition at each section is then computed and the cross section shape adjusted accordingly.
The computations then proceed to the next flow in the sequence and the cycle is repeated beginning with
the updated geometry. The sediment calculations are performed by grain size fraction thereby allowing for
the simulation of hydraulic sorting and armoring. Features of the model include: capability to analyze
networks of streams, automatic channel dredging, various levee and encroachment options, and several
options for computation of sediment transport rates.
Experience has shown that successful application of movable boundary models may require
substantial effort to reproduce field observations, i.e. calibration. This document complements the HEC-6
User's Manual (HEC, 1991) and provides guidelines for calibration and application. The general topic of
application and calibration of numerical river models is thoroughly covered in Cunge, et al. (1980).
This document provides guidance on the engineering aspects of applying HEC-6; it is, therefore, a
supplement to the HEC-6 User's Manual. Originally published in 1981, this edition contains substantial
new material based on program enhancements and applications experience gained since then.


This document was prepared by D. Michael Gee, Training Division, HEC. William A. (Tony)
Thomas, Hydraulics Laboratory, WES, provided most of the concepts and material included herein. Vern
Bonner was Chief, Training Division and Darryl W. Davis, Director, HEC, during preparation of this report.

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