DWOPER routing

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DWOPER is a dynamic wave flood routing model contained in NWSRFS that routes an inflow hydrograph to a point downstream.
It can be used on a single river or system of rivers where storage routing methods are inadequate due to the effects of backwater, tides, and mild channel bottom slopes.
The model is based on the complete one-dimensional St. Venant equations.

A weighted four-point non-linear implicit finite difference scheme is used to obtain solutions to the St. Venant equations via a Newton-Raphson iterative technique.

DWOPER has a number of features which make it applicable to a variety of natural river systems for real-time forecasting.
It is designed to accommodate various boundary conditions and irregular cross sections located at unequal distances along a single multiple-reach river or several such rivers having dendritic configurations.
DWOPER allows for roughness parameters to vary with location and stage or discharge.
Temporally varying lateral inflows, wind effects, bridge effects, off-channel storage, and weir-flow channel bifurcations to simulate levee overtopping are included among its features.
Time steps are chosen solely on the basis of desired accuracy since the implicit finite difference technique is not restricted to the very small time steps of explicit techniques due to numerical stability considerations.

This enables DWOPER to be very efficient as to computational time for simulating slowly varying floods of several days duration.