Seeking advice on increasing channel erosion for steep gully debris

Yukuner · 2026-01-30 16:35:37

I am simulating a debris flow event in a steep mountain gully (average slope > 10%) using the BASEHPC v4.2 (GPU) module. My objective is to study the cascading failure of multiple check dams and the subsequent erosion-induced discharge amplification.

The Problem:
In my current results, the channel shows extensive deposition (red) across almost the entire reach, with negligible erosion (blue) even in the steepest sections. This contradicts field observations and historical data for this gully, where significant down-cutting and bed-scouring are expected.

Current Setup Highlights:
Module: BASEHPC v4.2 (Double Precision).
Fluid Density: 1900 kg/m ³ (to represent hyper-concentrated flow).
Formula: MPM_multi with coefficient: 1.0 and exponent: 1.0.
Friction: Manning's n = 0.07 for the channel.
Sediment Boundary: equilibrium_in at the inflows.
Soil: Loose material defined with z_rel down to -5.0m or -10.0m.

My Questions:
1.Which parameters are most sensitive for increasing the scouring power of the flow? Should I significantly increase the bedload_factor or the coefficient in the MPM_multi block?
2.The coefficient is currently set to 1.0. Would increasing it to the standard value of 8.0 (or higher) be the correct approach for debris flows?
3.To achieve the "Hungry Water" effect (清水冲刷), should I switch the sediment boundary from equilibrium_in to transport_capacity with a low boundary_factor?
4.Are there any other limiters (like max_bed_change_rate) that I should check to ensure the model allows rapid erosion?

I have attached my model.json below for reference. Any suggestions on how to "calibrate" the model to show more realistic erosion would be greatly appreciated.

““{
"SETUP": {
"simulation_name": "NWG_Test_02_less_slump",
"BASEHPC": {
"PHYSICAL_PROPERTIES": {
"gravity": 9.81
},
"BASEPLANE_2D": {
"GEOMETRY": {
"STRINGDEF": [
{
"name": "Inflow_1",
"upstream_direction": "left"
},
{
"name": "Inflow_2",
"upstream_direction": "left"
},
{
"name": "Outflow",
"upstream_direction": "left"
},
{
"name": "NWG-D1-X1_dam-axis_3",
"upstream_direction": "left"
},
{
"name": "NWG-D2-Z1_dam-axis_7",
"upstream_direction": "left"
},
{
"name": "NWG-D3_dam-axis_10",
"upstream_direction": "left"
},
{
"name": "NWG-D4_dam-axis_12",
"upstream_direction": "left"
},
{
"name": "NWG-D5_dam-axis_14",
"upstream_direction": "left"
},
{
"name": "NWG-D6_dam-axis_18",
"upstream_direction": "left"
},
{
"name": "cross-section1",
"upstream_direction": "left"
},
{
"name": "cross-section2",
"upstream_direction": "left"
},
{
"name": "cross-section3",
"upstream_direction": "left"
},
{
"name": "cross-section4",
"upstream_direction": "left"
},
{
"name": "cross-section8",
"upstream_direction": "left"
},
{
"name": "cross-section9",
"upstream_direction": "left"
},
{
"name": "cross-section11",
"upstream_direction": "left"
},
{
"name": "cross-section12",
"upstream_direction": "left"
},
{
"name": "cross-section13",
"upstream_direction": "left"
},
{
"name": "cross-section14",
"upstream_direction": "left"
},
{
"name": "cross-section15",
"upstream_direction": "left"
},
{
"name": "cross-section16",
"upstream_direction": "left"
},
{
"name": "cross-section20",
"upstream_direction": "left"
},
{
"name": "cross-section21",
"upstream_direction": "left"
}
],
"REGIONDEF": [
{
"index": [
1
],
"name": "Channel"
},
{
"index": [
2
],
"name": "Bank"
},
{
"index": [
11
],
"name": "Dam_1"
},
{
"index": [
12
],
"name": "Dam_2"
},
{
"index": [
13
],
"name": "Dam_3"
},
{
"index": [
14
],
"name": "Dam_4"
},
{
"index": [
15
],
"name": "Dam_5"
},
{
"index": [
16
],
"name": "Dam_6"
},
{
"index": [
3
],
"name": "Channel_out1"
},
{
"index": [
4
],
"name": "Channel_out2"
},
{
"index": [
5
],
"name": "Deposit_area1"
},
{
"index": [
6
],
"name": "Deposit_area2"
},
{
"index": [
7
],
"name": "Channel_2"
},
{
"index": [
8
],
"name": "Channel_3"
}
],
"mesh_file": "NWG_Final.2dm"
},
"HYDRAULICS": {
"BOUNDARY": {
"STANDARD": [
{
"discharge_file": "Inflow_1.txt",
"name": "Inflow_1",
"slope": 0.074,
"string_name": "Inflow_1",
"type": "uniform_in"
},
{
"discharge_file": "Inflow_2.txt",
"name": "Inflow_2",
"slope": 0.117,
"string_name": "Inflow_2",
"type": "uniform_in"
},
{
"name": "Outflow",
"string_name": "Outflow",
"type": "zero_gradient_out"
}
]
},
"FRICTION": {
"type": "manning",
"default_friction": 0.07,
"regions": [
{
"friction": 0.07,
"region_name": "Channel"
},
{
"friction": 0.1,
"region_name": "Bank"
},
{
"friction": 0.1,
"region_name": "Channel_out1"
},
{
"friction": 0.25,
"region_name": "Channel_out2"
},
{
"friction": 0.3,
"region_name": "Deposit_area1"
},
{
"friction": 0.3,
"region_name": "Deposit_area2"
},
{
"friction": 0.07,
"region_name": "Channel_2"
},
{
"friction": 0.07,
"region_name": "Channel_3"
}
]
},
"INITIAL": {
"type": "dry"
},
"PARAMETER": {
"CFL": 0.6,
"fluid_density": 1900.0,
"max_time_step": 100,
"safe_mode": "off",
"max_velocity": 50.0,
"minimum_water_depth": 0.01
}
},
"MORPHOLOGY": {
"INITIAL": {
"type": "mesh"
},
"PARAMETER": {
"sediment_porosity": 0.26,
"sediment_density": 2650,
"morphodynamic_solver": "Upwind",
"upwind_factor": 0.8,
"morphodynamic_start": 0.0,
"ACTIVE_LAYER": {
"active_layer_type": "constant",
"active_layer_thickness": 0.05
}
},
"BEDMATERIAL": {
"GRAIN_CLASS": {
"diameters": [
0.001,
0.1,
0.5,
1.0,
2.0,
5.0,
10.0,
20.0,
50.0
]
},
"MIXTURE": [
{
"name": "mix1",
"volume_fraction": [
6.32,
29.93,
7.83,
4.26,
6.11,
11.86,
17.25,
11.95,
4.49
]
}
],
"SOILDEF": [
{
"LAYER": [
{
"mixture_name": "mix1",
"z_rel": -10.0
}
],
"name": "Soil_Thin"
},
{
"LAYER": [
{
"mixture_name": "mix1",
"z_rel": -10.0
}
],
"name": "Soil_Dam2"
},
{
"LAYER": [
{
"mixture_name": "mix1",
"z_rel": -10.0
}
],
"name": "Soil_Dam_Other"
},
{
"LAYER": [
{
"mixture_name": "mix1",
"z_rel": -5.0
}
],
"name": "gully_bank"
}
],
"SOIL_ASSIGNMENT": {
"default_soil": "gully_bank",
"regions": [
{
"region_name": "Bank",
"soil_name": "gully_bank"
},
{
"region_name": "Channel",
"soil_name": "Soil_Thin"
},
{
"region_name": "Dam_1",
"soil_name": "Soil_Dam_Other"
},
{
"region_name": "Dam_2",
"soil_name": "Soil_Dam2"
},
{
"region_name": "Dam_3",
"soil_name": "Soil_Dam_Other"
},
{
"region_name": "Dam_4",
"soil_name": "Soil_Dam_Other"
},
{
"region_name": "Dam_5",
"soil_name": "Soil_Dam_Other"
},
{
"region_name": "Dam_6",
"soil_name": "Soil_Dam_Other"
}
]
}
},
"BEDLOAD": {
"FORMULA": {
"factor": 1.0,
"type": "MPM_multi",
"theta_critical_approach": "constant",
"critical_value": 0.042,
"coefficient": 8.0,
"exponent": 1.0
},
"BOUNDARY": {
"STANDARD": [
{
"name": "Sed_In1",
"string_name": "Inflow_1",
"type": "equilibrium_in",
"mixture_name": "mix1",
"reference_bed_elevation": 1220.85
},
{
"name": "Sed_In2",
"string_name": "Inflow_2",
"type": "equilibrium_in",
"mixture_name": "mix1",
"reference_bed_elevation": 1217.34
},
{
"name": "Sed_Out",
"string_name": "Outflow",
"type": "equilibrium_out",
"reference_bed_elevation": 1050.12
}
]
}
},
"GRAVITATIONAL_TRANSPORT": {
"critical_angle_dry": 40.0,
"critical_angle_wet": 30.0,
"max_bed_change_rate": 0.5
}
}
}
}
}
}”

Thank you very much for your time and help!
Best regards,
Yukuner

Matteo Facchini · 2026-02-05 15:06:03

Hi
honestly I do not think that the shallow water equations are suited for modeling debris-flows.
Regardless of the parameters you can change, the equations are just not built for that purpose.
Cheers
Matteo

User Forum of Software BASEMENT

#1 2026-01-30 16:35:37

Seeking advice on increasing channel erosion for steep gully debris

#2 2026-02-05 15:06:03

Re: Seeking advice on increasing channel erosion for steep gully debris

Board footer