Assessing the perturbations of the hydrogeological regime in sloping fens due to roads
Date issued
February 1, 2020
In
Hydrology and Earth System Sciences
Vol
1
No
24
From page
213
To page
226
Reviewed by peer
1
Abstract
Roads in sloping fens constitute a hydraulic barrier for surface and subsurface flow. This can lead to the
drying out of downslope areas of the sloping fen as well
as gully erosion. Different types of road construction have
been proposed to limit the negative implications of roads on
flow dynamics. However, so far, no systematic analysis of
their effectiveness has been carried out. This study presents
an assessment of the hydrogeological impact of three types
of road structures in semi-alpine, sloping fens in Switzerland. Our analysis is based on a combination of field measurements and fully integrated, physically based modeling.
In the field approach, the influence of roads was examined
using tracer tests in which the area upslope of the road was
sprinkled with a saline solution. The spatial distribution of
electrical conductivity downslope provided a qualitative assessment of the flow paths and, thus, the implications of the
road structures on subsurface flow. A quantitative albeit not
site-specific assessment was carried out using fully coupled
numerical models jointly simulating surface and subsurface
flow processes. The different road types were implemented
and their influence on flow dynamics was assessed for a wide
range of slopes and different hydraulic conductivities of the
soil. The models are based on homogenous soil conditions,
allowing for a relative ranking of the impact of the road types.
For all cases analyzed in the field and simulated using the numerical models, roads designed with an L drain (i.e., collecting water upslope and releasing it in a concentrated manner
downslope) constitute the largest perturbations in terms of
flow dynamics. The other road structures investigated were
found to have less impact. The developed methodologies and
results can be used for the planning of future road projects in
sloping fens.
drying out of downslope areas of the sloping fen as well
as gully erosion. Different types of road construction have
been proposed to limit the negative implications of roads on
flow dynamics. However, so far, no systematic analysis of
their effectiveness has been carried out. This study presents
an assessment of the hydrogeological impact of three types
of road structures in semi-alpine, sloping fens in Switzerland. Our analysis is based on a combination of field measurements and fully integrated, physically based modeling.
In the field approach, the influence of roads was examined
using tracer tests in which the area upslope of the road was
sprinkled with a saline solution. The spatial distribution of
electrical conductivity downslope provided a qualitative assessment of the flow paths and, thus, the implications of the
road structures on subsurface flow. A quantitative albeit not
site-specific assessment was carried out using fully coupled
numerical models jointly simulating surface and subsurface
flow processes. The different road types were implemented
and their influence on flow dynamics was assessed for a wide
range of slopes and different hydraulic conductivities of the
soil. The models are based on homogenous soil conditions,
allowing for a relative ranking of the impact of the road types.
For all cases analyzed in the field and simulated using the numerical models, roads designed with an L drain (i.e., collecting water upslope and releasing it in a concentrated manner
downslope) constitute the largest perturbations in terms of
flow dynamics. The other road structures investigated were
found to have less impact. The developed methodologies and
results can be used for the planning of future road projects in
sloping fens.
Publication type
journal article
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