Sediment Transport and Morphological Change¶

NUMERICAL SCHEME

• Sed_Scheme: numerical scheme for solving the advection-diffusion equation

• Sed_Scheme = TVD: TVD scheme

• Sed_Scheme = Upwinding: Upwinding scheme (default)

SEDIMENT PARAMETERS

Non-cohesive

• D50: median grain diameter $$D_{50}$$, default $$D_{50} = 0.5mm$$

• Sdensity: gravity of sediment $$s$$, default $$s = 2.68$$

• n_porosity: porosity of sediment $$n$$, default $$n=0.47$$

• WS: settling velocity $$w_f$$, default $$w_f = 0.125$$ m/s

• Shields_cr: critical Shields parameter for suspended load $$\theta_{cr}$$, default $$\theta_{cr} = 0.05$$

• Shields_cr_bedload: Shields parameter for bedload $$\theta_{cr}^{b}$$, default $$\theta_{cr}^{b} = 0.047$$ based on Meyer-Peter and Muller (1984)

• Kappa1: Runge-Kutta parameter $$\kappa_1$$, default $$\kappa_1 = 0.3333$$, 4th-order

• Kappa2: Runge-Kutta parameter $$\kappa_2$$, default $$\kappa_1 = 1.0$$, 4th-order

• MinDepthPickup: the minimum depth for sediment pickup action. The purpose of this parameter is to avoid over-shooting at a very small depth. Default: MinDepthPickup = 0.1m.

Cohesive

• CohesiveSediment: flag for cohesive sediment, default FALSE

• k_coh: diffusion coefficient, default $$k = 10E-6$$ (different from the non-cohesive sediment transport)

• Tau_cr_coh: critical shear stress for erosion, default $$\tau_{cr} = 0.001$$

• Tau_crd_coh: critical shear stress for deposition, default $$\tau_{cd} = 0.001$$

• a_coh, b_coh, n_coh and m_coh: Empirical parameters used to calculate settling velocity, default values are $$a = 0.1$$, $$b = 2.0$$, $$n = 0.5$$, and $$m = 1.5$$

• E_coh: erodibility parameter, default $$E = 0.0001$$

• alpha_coh: alpha-coefficient used to calculate the erosion rate for soft bed, default $$\alpha = 1.0$$ (if SoftBed = T)

MORPHOLOGICAL CHANGE

• Bed_Change: logical parameter, T: update depth, F: no bed change.

• Hard_bottom: logical parameter, T: hard bed, no erosion allowed, F: sediment bed

• Hard_bottom_file: the file contains the distribution of the erodible layer thickness, $$Z_s$$. Zero or a negative value represents ‘non-erodible’. For example, $$Z_s = 0.1$$ means the bed can be eroded at most 0.1 m. The format is the same as the depth file.

Note

The previous version before 3.4 used the hard bottom masks rather than erodible thickness.

• Morph_step: ratio of Boussinesq model time step to the morphological updating step, $$dt_{morph}$$, default: $$dt_{morph}$$ = 25

AVALANCHE

• Avalanche: logical parameter, T: consider avalanche, F: not consider avalanche

• Tan_phi: tangent of the repose angle $$\tan \phi$$, default $$\tan \phi = 0.7$$, or 35 deg

OUTPUT

• PLOT_INTV_SEDIMENT: time interval for plotting sediment transport variables, default is the same as the Boussinesq model (PLOT_INTV)

• C_xxxxx: Sediment concentration (g/l) at xxxxx output step

• Pick_xxxxx: sediment pickup value at xxxxx output step

• Depo_xxxxx: sediment deposition value at xxxxx output step

• DchgS_xxxxx: depth change (without considering porosity) due to suspended load UPTO xxxxx output step

• DchgB_xxxxx: depth change (without considering porosity) due to bedload UPTO xxxxx output step

• BedFx_xxxxx: bedload flux in x

• BedFy_xxxxx: bedload flux in y

• dep_xxxxx: depth (with considering porosity) UPTO xxxxx output step

• BedStr_xxxxx: bed shear stress (non-dimensional) UPTO xxxxx output step; multiply by $$\rho_w$$ to convert to physical value of $$\tau_b$$