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BASEMENT
Basic Simulation Environment for computation of environmental flow and natural hazard simulation
Laboratory of Hydraulics, Hydrology and Glaciology (VAW)
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#1 2020-09-03 09:30:10

Alyssa
User
From: Aix-en-Provence, France
Registered: 2019-10-28
Posts: 41

Dredging under fixed bed level (sediment mining)

Hi

My river has had sediment mining in the past and I would need to model the impact of this in 1D (e.g. did it cause aggradation downstream of the mining place, how did grain size distribution changed of the bed,...). I have a volume (560000m3) that was locally taken from the bed.

I understand the 'dredge' function cannot be used for simulating this, since it doesn't go below the fixed bed.
How could I do this in Basement? What about a negative sediment_discharge? It seems with that there is an option to include erode_below_fixed_bed. Would that work? I see there is a warning of this function that it might lead to unclear behaviour..

Thanks for your help

Alyssa

Last edited by Alyssa (2020-09-03 09:31:34)

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#2 2020-09-03 16:26:54

Matteo Facchini
Developer
From: Trento
Registered: 2014-09-05
Posts: 284

Re: Dredging under fixed bed level (sediment mining)

Hi Alyssa,

do you need to simulate this process during the simulation, or could it be a pre-processing process?

In this case, you could modify your geometry to have the sediment removed. If you need to study the dynamic of the river during the extraction, you could set a deeper fixed bed where you need to dredge.

I would avoid the negative sediment discharge, because it could cause instabilities in the fluxes calculations!

Hope this helps,
Matteo

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#3 2020-09-04 09:37:02

Alyssa
User
From: Aix-en-Provence, France
Registered: 2019-10-28
Posts: 41

Re: Dredging under fixed bed level (sediment mining)

Hi Matteo

Thanks for the reply smile
I thought about changing the geometry as an option. What do you mean by setting a deeper fixed bed? I thought you can only do that by changing the geometry, isn't the fixed bed defined by that?
I have 1 soil with 2 layers (surface and subsurface which is very deep).

Bye
Alyssa

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#4 2020-09-07 07:51:59

Matteo Facchini
Developer
From: Trento
Registered: 2014-09-05
Posts: 284

Re: Dredging under fixed bed level (sediment mining)

Hi Alyssa,

you can define a soil in the geometry and define different indeces for each soil using e.g. the slices. Then, you can use this definition under SOIL_ASSIGNMENT in the bmc file and define different soils based on the indeces. Each soil can have different layers and if you set a layer with bottom_elevation=0.0 you are basically defining a fixed bed layer!

Hope this helps,
Matteo

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#5 2020-09-11 12:38:47

Alyssa
User
From: Aix-en-Provence, France
Registered: 2019-10-28
Posts: 41

Re: Dredging under fixed bed level (sediment mining)

Hi Matteo

I have  assigned a soil as you mentioned for the area of the active bed. In soil assignment I used 2 layers for this soil, a surface (-0.1m) and subsurface(until -5m). Still it tells me the fixed bed is at the top of the bed so dredging is not possible.

thanks
Alyssa

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#6 2020-09-11 13:51:40

Matteo Facchini
Developer
From: Trento
Registered: 2014-09-05
Posts: 284

Re: Dredging under fixed bed level (sediment mining)

Hey Alyssa,

have you defined a soil over the entire width of the cross-section? If not, try to do that!

Cheers,
Matteo

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#7 2020-10-09 17:55:37

Alyssa
User
From: Aix-en-Provence, France
Registered: 2019-10-28
Posts: 41

Re: Dredging under fixed bed level (sediment mining)

Hi Matteo

I tried again with rectangular cross sections to make it easier, and the entire width of the section now has the same soil (consisting of 2 layers). The error remains however:

" Dredge level '122' is below the fixed bed elevation of '124.946' in cross section 'PK65'. Dredging of the fixed bed is not allowed. .."

What is also strange is that my bed level at this cross section is 124.53, so I don't know what is this value of 124.946. And why is it seen as fixed bed?


Thanks

Alyssa

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#8 2021-03-08 10:20:50

Matteo Facchini
Developer
From: Trento
Registered: 2014-09-05
Posts: 284

Re: Dredging under fixed bed level (sediment mining)

Hi Alyssa,
it is hard to know without looking at the geometry. Would you mind pasting here the cross-section definition from the bmg file?

Or, if you solved the problem, woud you mind writing here how you did it?

Best
Matteo

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#9 2021-05-27 11:08:12

Alyssa
User
From: Aix-en-Provence, France
Registered: 2019-10-28
Posts: 41

Re: Dredging under fixed bed level (sediment mining)

Hi Matteo

No I never solved this issue, I just changed the geometry of the bed. But it would be nice to know how to use this function. The .bmg I had for this exercise is copied below. I'm using rectangular cross sections. I also copied the part of the code where I define the soil and layers.
Thanks

CROSS_SECTION {
	name           = PK52
	distance_coord = 0
	node_coords    = ((0,151.4), (5,131.4), (155,131.4), (160,151.4))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK52_5
	distance_coord = 0.5
	node_coords    = ((0,151.1), (5,131.2), (155,131.2), (160,151.1))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK53
	distance_coord = 1
	node_coords    = ((0,150.8), (5,130.86), (155,130.86), (160,150.8))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK54
	distance_coord = 2
	node_coords    = ((0,150.3), (5,130.32), (155,130.32), (160,150.3))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK55
	distance_coord = 3
	node_coords    = ((0,149.8), (5,129.82), (155,129.82), (160,149.8))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK56
	distance_coord = 4
	node_coords    = ((0,149.2), (5,129.25), (155,129.25), (160,149.2))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK57
	distance_coord = 5
	node_coords    = ((0,148.7), (5,128.74), (155,128.74), (160,148.7))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK58
	distance_coord = 6
	node_coords    = ((0,148.2), (5,128.22), (155,128.22), (160,148.2))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK59
	distance_coord = 7
	node_coords    = ((0,147.7), (5,127.72), (155,127.72), (160,147.7))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK60
	distance_coord = 8
	node_coords    = ((0,147.1), (5,127.15), (155,127.15), (160,147.1))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK60_50
	distance_coord = 8.50
	node_coords    = ((0,147.1), (5,126.9), (155,126.9), (160,147.1))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK60_51
	distance_coord = 8.51
	node_coords    = ((0,147.1), (5,126.9), (155,126.9), (160,147.1))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK61
	distance_coord = 9
	node_coords    = ((0,146.6), (5,126.64), (155,126.64), (160,146.6))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK62
	distance_coord = 10
	node_coords    = ((0,146.09), (5,126.11), (155,126.11), (160,146.09))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK63
	distance_coord = 11
	node_coords    = ((0,145.6), (5,125.61), (155,125.61), (160,145.6))
	bottom_range   = (5,155)
	SOIL_DEF {
		index = 1
		range = (5,155)
	}
}
CROSS_SECTION {
	name           = PK64
	distance_coord = 12
	node_coords    = ((0,145.0), (5,125.04), (235,125.04), (240,145.0))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK65
	distance_coord = 13
	node_coords    = ((0,144.5), (5,124.53), (235,124.53), (240,144.5))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK66
	distance_coord = 14
	node_coords    = ((0,144), (5,124.01), (235,124.01), (240,144))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK67
	distance_coord = 15
	node_coords    = ((0,143.46), (5,123.48), (235,123.48), (240,143.46))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK68
	distance_coord = 16
	node_coords    = ((0,142.9), (5,122.92), (235,122.92), (240,142.9))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK69
	distance_coord = 17
	node_coords    = ((0,142.4), (5,122.42), (235,122.42), (240,142.4))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK70
	distance_coord = 18
	node_coords    = ((0,141.8), (5,121.84), (235,121.84), (240,141.8))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK71
	distance_coord = 19
	node_coords    = ((0,141.4), (5,121.41), (235,121.41), (240,141.4))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK72
	distance_coord = 20
	node_coords    = ((0,140.83), (5,120.81), (235,120.81), (240,140.83))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK73
	distance_coord = 21
	node_coords    = ((0,140.3), (5,120.33), (235,120.33), (240,140.3))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK74
	distance_coord = 22
	node_coords    = ((0,139.7), (5,119.73), (235,119.73), (240,139.7))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK75
	distance_coord = 23
	node_coords    = ((0,139.3), (5,119.31), (235,119.31), (240,139.3))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK76
	distance_coord = 24
	node_coords    = ((0,138.7), (5,118.71), (235,118.71), (240,138.7))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK77
	distance_coord = 25
	node_coords    = ((0,138.2), (5,118.23), (235,118.23), (240,138.2))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK78
	distance_coord = 26
	node_coords    = ((0,137.7), (5,117.7), (235,117.7), (240,137.7))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK79
	distance_coord = 27
	node_coords    = ((0,137.1), (5,117.15), (235,117.15), (240,137.1))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK80
	distance_coord = 28
	node_coords    = ((0,136.6), (5,116.63), (235,116.63), (240,136.6))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK81
	distance_coord = 29
	node_coords    = ((0,136.1), (5,116.12), (235,116.12), (240,136.1))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}
CROSS_SECTION {
	name           = PK82
	distance_coord = 30
	node_coords    = ((0,135.57), (5,115.57), (235,115.57), (240,135.57))
	bottom_range   = (5,235)
	SOIL_DEF {
		index = 2
		range = (5,235)
	}
}

----------------------------------------------

			BEDMATERIAL {
				GRAIN_CLASS {
					diameters = (2.0 5.7 11.3 22.6 45.3 76.1 107.6 151.8 214.7 277.1)
				}
				MIXTURE {
					name            = surface
					volume_fraction = (0.22 0.73 7.62 25.83 27.78 16.69 13.22 4.72 2.89 0.30)
				}
				MIXTURE {
					name            = subsurface
					volume_fraction = (1.99 3.03 18.32 35.77 27.76 10.18 2.75 0.18 0.01 0.01)
				}
				SOIL_ASSIGNMENT {
					index = (1)
					soil  = (soil1)
					type  = index_table
				}
				SOIL_DEF {
					name = soil1
					LAYER {
						mixture          = surface
						bottom_elevation = -0.1
					}
					LAYER {
						mixture          = subsurface
						bottom_elevation = -5
					}
				}
			}

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#10 2021-06-03 14:53:41

Matteo Facchini
Developer
From: Trento
Registered: 2014-09-05
Posts: 284

Re: Dredging under fixed bed level (sediment mining)

Hi Alyssa,
try also to set the active range same as the bottom range.
Cheers
Matteo

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