6.15. `jules_rivers.nml`¶

This file sets the river routing options. It contains two namelists called JULES_RIVERS and JULES_OVERBANK.

Note

The river routing code in JULES is still in development. Users should ensure that results are as expected, and provide feedback where deficiencies are identified.

6.15.1. `JULES_RIVERS` namelist members¶

JULES_RIVERS::l_rivers¶

Type:	logical
Default:	F

Switch for enabling river routing.

TRUE: Use the river routing algorithm specified by i_river_vn to route runoff along river pathways.
FALSE: No river routing.

JULES_RIVERS::i_river_vn¶

Type:	integer
Default:	rfm

Switch to select the river routing algorithm to use for river routing.

1: Use a UM-coupled JULES implementation of the TRIP model (see Oki et al. 1999). This value is not allowed in standalone JULES
2: Use a standalone JULES implementation of the RFM kinematic wave model (see Dadson and Bell 2010, Bell et al. 2007).
3: Use a standalone JULES implementation of the TRIP model (see Oki et al. 1999).

JULES_RIVERS::nstep_rivers¶

Type:	integer
Permitted:	> 0
Default:	-32768

The number of model timesteps per routing timestep.

For example, nstep_rivers = 5 means that runoff will be accumulated for 5 model timesteps before being routed on the 5th timestep.

Warning

The river routing parameter values can be highly dependent on model resolution, so care is required by the user to ensure that appropriate values are selected, tested and adjusted as required.

Suggested values for global and high-resolution runs are listed below, however these should be treated as a starting point only.

Values for some typical configurations are included in the jules_riversparm module.

RFM parameters - used if i_river_vn = 2

JULES_RIVERS::cland¶

Type:	real
Default:	0.20 m/s
Suggested:	0.20 m/s (global), 0.40 m/s (1 km resolution, Bell et al. 2007)

The land wave speed (kinematic wave speed for surface flow in a land grid box on the river routing grid, m s^-1). This is the speed at which water moves through surface soil in a non-river grid cell (even without major rivers, there are always minor water courses so these cells do still contribute flow to neighbouring cells).

JULES_RIVERS::criver¶

Type:	real
Default:	0.62 m/s
Suggested:	0.62 m/s (global), 0.50 m/s (1 km resolution, Bell et al. 2007)

The river wave speed (kinematic wave speed for surface flow in a river grid box on the river routing grid, m s^-1). This value should be close to the rivers_speed used by TRIP, but not identical because RFM makes different assumptions about e.g. meandering.

JULES_RIVERS::cbland¶

Type:	real
Permitted:	<= `cland`
Default:	0.10 m/s
Suggested:	0.10 m/s (global), 0.05 m/s (1 km resolution, Bell et al. 2007)

The subsurface land wave speed (kinematic wave speed for subsurface flow in a land grid box on the river routing grid, m s^-1).

JULES_RIVERS::cbriver¶

Type:	real
Permitted:	<= `criver`
Default:	0.15 m/s
Suggested:	0.15 m/s (global), 0.05 m/s (1 km resolution, Bell et al. 2007)

The subsurface river wave speed (kinematic wave speed for subsurface flow in a river grid box on the river routing grid, m s^-1).

JULES_RIVERS::retl¶

Type:	real
Permitted:	(-1)-(+1)
Default:	0.0
Suggested:	0.005 (1 km resolution, Bell et al. 2007)

The (resolution dependent) land return flow fraction. Bell et al. (2007:Table1) suggested value 0.005. On non-river grid cells in the land mask: if retl>0 then fraction retl of the subsurface flow moves to the surface per routing timestep; if retl<0 then fraction retl of the surface flow moves to the subsurface per routing timestep.

JULES_RIVERS::retr¶

Type:	real
Permitted:	(-1)-(+1)
Default:	0.005
Suggested:	0.005 (1 km resolution, Bell et al. 2007)

The (resolution dependent) river return flow fraction. On river grid cells in the land mask: if retr>0 then fraction retr of the subsurface flow moves to the surface per routing timestep; if retr<0 then fraction retr of the surface flow moves to the subsurface per routing timestep.

JULES_RIVERS::a_thresh¶

Type:	integer
Default:	1
Suggested:	1 (spatial resolution coarser than 20 km gridcells), ~10 (high-resolution)

The threshold drainage area (specified in number of cells) draining to a gridbox, above which the grid cell is considered to be a river point (see a_T in Bell et al. 2007:541). Remaining points are treated as land (drainage area = 0) or sea (drainage area < 0).

Remaining points are treated as land (drainage area = 0) or sea (drainage area < 0). See Bell et al. (2007).

JULES_RIVERS::runoff_factor¶

Type:	real
Default:	1.0

Values !=1.0 are generally used to correct biases in precipitation when the model is forced with observed data It is highly recommended that this is set to 1.0 (i.e. no runoff adjustment).

TRIP parameters - used if i_river_vn = 1,3

JULES_RIVERS::rivers_speed¶

Type:	real
Default:	0.4

The effective river velocity (m s^-1). See Oki et al. (1999). rivers_speed should equal (river flow velocity / rivers_meander).

JULES_RIVERS::rivers_meander¶

Type:	real
Default:	1.4

The ratio of the actual to calculated river lengths in a river routing gridbox. See Oki et al. (1999).

6.15.2. `JULES_OVERBANK` namelist members¶

Warning

The overbank inundation parameter values can be highly dependent on model resolution, so care is required by the user to ensure that appropriate values are selected, tested and adjusted as required.

Suggested values for global and high-resolution runs are listed below, however these should be treated as a starting point only.

JULES_OVERBANK::l_riv_overbank¶

Type:	logical
Default:	F

Switch for enabling river overbank inundation. Only used if l_rivers is TRUE.

TRUE: Calculate frac_fplain_lp, i.e. overbank inundation area as a fraction of gridcell area.
FALSE: No overbank inundation calculations

Note

If l_riv_overbank = FALSE, no further variables are needed from this namelist.

JULES_OVERBANK::l_riv_hypsometry¶

Type:	logical
Default:	F

Switch for enabling use of a hypsometric integral calculation.

TRUE: Calculate inundated area from a hypsometric integral based on a lognormal area-altitude distribution (recommended).
FALSE: Estimate inundated area from simple river width scaling, ignoring topography (only to be used for testing).

River depth allometry (used if l_riv_hypsometry is TRUE or use_rosgen is TRUE)

Allometry is: (DEPTH in m) = riv_c * ( (SURFACE RIVER INFLOW in m3 s^-1) ^ riv_f) (Leopold & Maddock 1953:eqn2)

JULES_OVERBANK::riv_c¶

Type:	real
Default:	none
Permitted:	>=0 and <=(1/`riv_a`)
Suggested:	0.27 (global, from Andreadis et al. 2013)

Coefficient in the allometry for river depth (units are (m / ((m3/s)^riv_f)), i.e. dependent on the value of riv_f)

JULES_OVERBANK::riv_f¶

Type:	real
Default:	none
Permitted:	>=0 and <=(1-`riv_b`)
Suggested:	0.30 (global, from Andreadis et al. 2013)

Exponent in the allometry for river depth (dimensionless)

River width scaling (used if l_riv_hypsometry is FALSE)

River width allometry

Allometry is: (WIDTH in m) = riv_a * ( (SURFACE RIVER INFLOW in m3 s^-1) ^ riv_b) (Leopold & Maddock 1953:eqn1)

JULES_OVERBANK::riv_a¶

Type:	real
Default:	none
Permitted:	>=0 and <=(1/`riv_c`)
Suggested:	7.20 (global, from Andreadis et al. 2013)

Coefficient in the allometry for river width (units are (m / ((m3/s)^riv_b)), i.e. dependent on the value of riv_b)

JULES_OVERBANK::riv_b¶

Type:	real
Default:	none
Permitted:	>=0 and <=(1-`riv_f`)
Suggested:	0.50 (global, from Andreadis et al. 2013)

Exponent in the allometry for river width (dimensionless)

JULES_OVERBANK::use_rosgen¶

Type:	logical
Default:	F

Switch for applying the Rosgen entrenchment ratio approach to estimate river width

TRUE: When inflow rates are lower than bankfull flow, river width is calculated from the River width allometry (above). However, when higher than bankfull flow, river width is constrained so that when river depth = 2 x bankfull depth then width = ent_ratio * bankfull width.
FALSE: River width follows the allometry specified above whatever the inflow rate.

Bankfull flow allometry (used if use_rosgen is TRUE) (Rosgen 1994)

Allometry is: (BANKFULL DISCHARGE RATE QBF in m3 s^-1) = coef_b * ( (CONTRIBUTING AREA in km2) ^ exp_c ) (see e.g. Andreadis et al. 2013)

JULES_OVERBANK::coef_b¶

Type:	real
Default:	none
Suggested:	0.08 (for “several drainages in western Washington State, USA”, Cragun 2005)

Coefficient in the allometry for bankfull flow (see Sen 2018:eqn3.33).

JULES_OVERBANK::exp_c¶

Type:	real
Default:	none
Suggested:	0.95 (for “several drainages in western Washington State, USA”, Cragun 2005)

Exponent in the allometry for bankfull flow (see Sen 2018:eqn3.33).

JULES_OVERBANK::ent_ratio¶

Type:	real
Default:	none

The Rosgen entrenchment ratio (single value for all water courses in the simulation): when river depth = 2 x bankfull depth then width = ent_ratio * bankfull width (i.e. ent_ratio can be used to specify how wide floodplains are allowed to be).

6.15. `jules_rivers.nml`¶

6.15.1. `JULES_RIVERS` namelist members¶

6.15.2. `JULES_OVERBANK` namelist members¶

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6.15. jules_rivers.nml¶

6.15.1. JULES_RIVERS namelist members¶

6.15.2. JULES_OVERBANK namelist members¶

6.15. `jules_rivers.nml`¶

6.15.1. `JULES_RIVERS` namelist members¶

6.15.2. `JULES_OVERBANK` namelist members¶