Geoscience Reference
In-Depth Information
1-D numerical models
1-D models simulate the flow and sediment transport in the streamwise direction of
a channel without solving the details over the cross-section. They are often applied
in the study of long-term sedimentation problems in rivers, reservoirs, estuaries, etc.
Described in this chapter are approaches and issues regarding 1-D models, such as
channel network routing, decoupled and coupled flow and sediment calculations, non-
uniform total-load transport, equilibrium and non-equilibrium sediment transport,
lateral allocation of bed change, bank erosion, data requirements, and parameter
sensitivity.
5.1 FORMULATION OF 1-D DECOUPLED FLOW
AND SEDIMENT TRANSPORT MODEL
As discussed in Section 2.2.3, in the case of low sediment concentration, the influence
of sediment on the flow field is negligible, and thus the simulation of the water and
sediment two-phase flow can be simplified as a problem of solving the clear water
flow with sediment transport. Moreover, because the bed usually changes at a much
lower rate than the flow (especially when bed load is the main transport mode), the
bed elevation can be assumed to be “fixed” at each time step, and the flow can be cal-
culated based on the channel geometry estimated at the previous time step. With these
simplifications, the flow and sediment calculations can be performed in a decoupled
manner. Such decoupled calculations are introduced in Sections 5.1-5.3.
5.1.1 Formulation of 1-D clear water flow model
5.1.1.1 1-D hydrodynamic equations
Dynamic wave model
In the 1-D dynamic wave model, open-channel flows are governed by Eqs. (2.102) and
(2.104), which are called the St. Venant equations. In the case with side flows (inflow
and/or outflow), these equations are written as
∂
A
t
+
∂
Q
x
=
q
l
(5.1)
∂
∂
