rivr (version 1.2-3)

route_wave: Flood wave routing

Description

Route a flood wave down a prismatic channel.

Usage

route_wave(
  So,
  n,
  Cm,
  g,
  B,
  SS,
  initial.condition,
  boundary.condition,
  downstream.condition,
  timestep,
  spacestep,
  numnodes,
  monitor.nodes,
  monitor.times,
  engine = c("Dynamic", "Kinematic"),
  scheme = c("MacCormack", "Lax"),
  boundary.type = c("QQ", "Qy", "yQ", "yy")
)

Arguments

So

Channel slope [\(L L^{-1}\)].

n

Manning's roughness coefficient.

Cm

Unit conversion coefficient for Manning's equation. For SI units, Cm = 1.

g

Gravitational acceleration [\(L T^{-2}\)].

B

Channel bottom width [\(L\)].

SS

Channel sideslope [\(L L^{-1}\)].

initial.condition

The initial flow rate [\(L^3 T^{-1}\)], assumed constant throughout the channel.

boundary.condition

Vector specifying the upstream boundary condition for the full duration of the model. If engine = "Kinematic", values are assumed to be flow [\(L^3 T^{-1}\)]. If engine = "Dynamic", the form of the boundary condition is determined by the argument boundary.type.

downstream.condition

Only used if engine = "Dynamic". Vector specifying the upstream boundary condition for the full duration of the model. Must be the same length as boundary.condition.

timestep

Temporal resolution of the model. Also the assumed time interval [\(T\)] between elements of boundary.condition and downstream.condition. The user is responsible for ensuring numerical stability.

spacestep

the spatial resolution of the model, interpreted as the distance [\(L\)] between nodes in the model domain. The user is responsible for ensuring numerical stability.

numnodes

The number of nodes used to discretize the channel. The total channel extent is computed as spacestep*(numnodes - 1).

monitor.nodes

the nodes to be monitored every time step. Specified as a vector of node indices, with 1 being the upstream boundary and numnodes being the downstream boundary.

monitor.times

the time steps at which to monitor every node. Specified as a vector of indices of boundary.condition. Defaults to five equally-spaced time steps including the first and last time steps.

engine

The engine to be used for routing the flood wave. May be either "Kinematic" or "Dynamic".

scheme

Only used if engine = "Dynamic". Specifies whether to use the Lax Diffusive scheme or the MacCormack predictor-corrector scheme.

boundary.type

Only used if engine = "Dynamic". Specifies what boundary data is supplied. Possible characters are If boundary.type = "QQ", both boundary.condition and downstream.condition are assumed to be flows [\(L^3 T^{-1}\)]. If boundary.type = "Qy" the upstream boundary is assumed to be flow while the downstream boundary is assumed to be depth [\(L\)]. Other possibilities are "yQ" and "yy".

Value

data.frame with columns:

step

Time step.

node

Node index.

time

Time since start.

distance

Downstream distance.

flow

Flow rate.

depth

Flow depth.

velocity

Flow velocity.

area

Flow area.

monitor.type

Row refers to a monitored node ("node") or timestep ("timestep").

Details

Provides implementations of a Kinematic Wave Model (KWM) and a Dynamic Wave Model (DWM) with the choice of two numerical schemes. The MacCormack scheme is a second-order accurate predictor-corrector scheme that provides efficient flood wave routing. The Lax diffusive scheme can be used to obtain smooth solutions for problems with discontinuities in the boundary conditions, e.g. sudden gate closures. The DWM implementation uses the Method of Characteristics (MOC) to compute the flow regime at the model boundaries, and allows the user to specify boundaries in terms of depths and/or flows. the KWM implementation assumes the normal depth at the upstream boundary and is only first-order accurate.

Examples

# NOT RUN {
# kinematic wave routing
times = seq(0, 30000, by = 25)
floodwave = ifelse(times >= 9000, 250,
  250 + (750/pi)*(1 - cos(pi*times/(60*75))))
route_wave(0.001, 0.045, 1.486, 32.2, 100, 0, initial.condition = 250, 
  boundary.condition = floodwave, timestep = 25, spacestep = 50, 
  numnodes=301, monitor.nodes = c(1, 101, 201, 301), 
  monitor.times = seq(1, length(times), by = 10), engine = "Kinematic")
# dynamic wave routing with zero-gradient downstream condition using MacCormack scheme
route_wave(0.001, 0.045, 1.486, 32.2, 100, 0, initial.condition = 250, 
  boundary.condition = floodwave, downstream.condition = rep(-1, length(times)), 
  timestep = 25, spacestep = 500, numnodes = 31, engine = "Dynamic", 
  scheme = "MacCormack", monitor.nodes = c(1, 11, 21, 31), 
  monitor.times = seq(1, length(times), by = 10))
# mixed boundary conditions (sudden gate closure) using Lax scheme
lax = route_wave(0.00008, 0.013, 1, 9.81, 6.1, 1.5, 
  initial.condition = 126, boundary.condition = rep(5.79, 2001), 
  downstream.condition = rep(0, 2001), timestep = 1, spacestep = 10, 
  numnodes = 501, monitor.nodes = c(1, 151, 251, 301, 501), 
  monitor.times = c(1, 501, 1001, 1501, 2001), 
  engine="Dynamic", scheme="Lax", boundary.type="yQ")
# extract data for a monitored point
require(dplyr)
filter(lax, monitor.type == "node", node == 151)
# }