modelling soil erosion and sediment transport on post mine...
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Soil and water conservation unit, TU Bergakademie Freiberg Agricolastr. 22, 09599 Freiberg, Germany
email: [email protected]
Modelling Soil Erosion and Sediment Transport on Post Mine Sites
Franziska Kunth, Jürgen Schmidt
MEDFRIEND Istanbul, 16 November 2012
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Introduction Methods Results Conclusion
www.lmbv.de
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Introduction Methods Results Conclusion
www.lmbv.de
Berlin
Study area
www.fkg.goe.ni.schule.de
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Introduction Methods Results Conclusion
www.lmbv.de
removal of overlying burden material
leads to formation of extensive spoil-
piles with steep slopes
Impacts have to be rehabilitated into
stabile self sustaining eco-systems with
no off-site pollution
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Severe soil losses on fragile, water
repellent and non-vegetated soils of
post mine sites
Erosion processes are strongly involved
in acidification of surface waters
Long-term renaturation of mine sites needs reliable assessment of soil erosion risks
Introduction Methods Results Conclusion
Motivation:
www.lr-online.de
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Development of a model based
methodology to determine erosion
risks on slopes in recultivation areas
Implementation of special soil
characteristics of coal-containing
mine sites (e.g. water repellency)
in the soil erosion model
EROSION 3D
Applying the EROSION 3D model to plan, dimension and test erosion
control measures on post mining landscapes
Introduction Methods Results Conclusion
Objectives:
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Event and raster-based physical soil erosion model
(cellular automata type)
Prediction of runoff and particle detachment, transport and deposition
Infiltration modelling according to GREEN&T (1911) approach
Momentum flux approach by SCHMIDT (1996) describes particle detachment
and transport
Computer model
Introduction Methods Results Conclusions Introduction Methods Results Conclusion
Model input-parameters:
Relief data
Rainfall data
Soil parameters (e.g. bulk density, grain size, calibration
factors, etc.)
Model output-parameters:
Spatial parameters
Cross section parameters
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Introduction Methods Results Conclusion
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Introduction Methods Results Conclusion
Rainfall simulator: - Three linked rainfall modules (height: 2 m, plot size: 3x1 m)
- Each with VeeJet Nozzles 80/100
- Runoff and sediment are collected
- Two steps: infiltration and erosion experiment
- Runoff feeding device allows simulation of variable virtual
lenght of slope up to 50 m (SCHINDEWOLF, 2012)
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Introduction Methods Results Conclusion
Water repellency effects occuring during rainfall experiments on coal containing post mine sites
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Water repellency reduces
infiltration to a minimum Rainfall intensity: 0,6 mm/min
Rainfall duration: 1 h
Wetting front infiltrates
less than 0,5 cm
Rainfall experiments on coal containing post mine sites
Introduction Methods Results Conclusion
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Experimentally determined EROSION 2D/3D calibration factors:
Rainfall experiments on coal containing post mine sites
* Data from "Parameter catalogue of Saxony" (Michael, 2000) for dry and sandy ploughed land
Introduction Methods Results Conclusion
0.00013 0.05
0.62
1
0
0.2
0.4
0.6
0.8
1
Skinfactor (-) Water repellency factor (-)
Water repellent post minesite
Reference plot*
0
0.1
0.2
0.3
0.4
0.5
1 6 11 16 21 26 31 36 41 46 51 56Rainfall duration [min]
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Comparison of measured infiltration rate and E2D/3D-simulated infiltration curve
Infil
tratio
n [m
m/m
in]
Calibration of calculated infiltration rates by water repellency factor
Introduction Methods Results Conclusion
Infiltration [mm/min]: Rainfall experiment
Simulation (with skin-factor) --- Simulation (with skin-factor and water repellency factor)
Soil cover: 0 % Slope: 9,3 % Bulk density: 1,2 g/m³ TOC: 3,6 M.% Initial soil moisture: 21,5 Vol. % Soil type: poor silty sand Skin-factor = 0,00013 Water repellency factor = 0,05
Effect of water repellency
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Comparison of infiltration rates and sediment concentrations: with/without soil crust
Rainfall experiment on crusted mine sites
Introduction Methods Results Conclusion
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Comparison of infiltration rates and sediment concentrations: with/without soil crust
Rainfall experiment on crusted mine sites
Introduction Methods Results Conclusion
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Comparison of infiltration rates and sediment concentrations: with/without soil crust (rainfall intensity: 0,63 mm/min)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 20 40 60
Infil
tratio
n [m
m/m
in]
Rainfall duration [min]
Infiltration with crust[mm/min]Infiltration without crust[mm/min]
With soil crust
Rainfall experiment on crusted mine sites
Infiltration: Sediment concentration:
Introduction Methods Results Conclusion
0
20
40
60
80
100
120
140
0 1 2 3 4 5 6 7 8 9 10 11S
edim
ent c
once
ntra
tion
[g/l]
Rainfall duration [min]
With soil crust
Without soil crust Without soil crust
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Sediment transport strongly
depends on surface conditions
Concerning post mine sites:
Biological soil crusts
Water repellency
Lack of vegetation
Introduction Methods Results Conclusion
Conclusions
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Water repellency contributes to increased surface runoff
Concentrated runoff in surface depressions produces high erosion rate
Calibration factor for water repellency enables use of EROSION 3D for
modelling erosion processes on post minesites
Introduction Methods Results Conclusion
Conclusions
Thank you for your attention!
Franziska Kunth
Soil and water conservation unit, TU Bergakademie Freiberg Agricolastr. 22, 09599 Freiberg, Germany email: [email protected]