Title: Assessing the reduction of the hydrological connectivity of gully systems through vegetation restoration: field experiments and numerical modelling
Authors: Molina Verdugo, Armando ×
Govers, Gerard
Van den Putte, An
Poesen, Jean
Vanacker, Veerle #
Issue Date: 2009
Publisher: European Geophysical Society
Series Title: Hydrology and Earth System Sciences vol:13 pages:1823-1836
Abstract: Restoration of degraded land in the Southern Ecuadorian Andes has led to alterations in the functioning of degraded catchments. Recovery of vegetation on areas affected by overgrazing, as well as the reforestation or afforestation
of gully areas have given rise to modifications of
hydrological connectivity within the catchments. Recent research has highlighted the ability of gully channels to trap sediment eroded from steep slopes, especially if vegetation is established along the gully bed. However, vegetation cover not only induces sediment deposition in the gully bed, but may also have a potential to reduce runoff water volume. The performance of gully beds in reducing the transfer of runoff was investigated by conducting controlled concentrated flow experiments in the field. Experimental field data for nine gullies were derived by pouring concentrated inflow into the upstream
end and measuring the outflow at the downstream end
of the channel. Two consecutive flow experiments per gully
were carried out, so that data for dry and wet soil conditions were collected. The hydrological response to concentrated flow was estimated for each experiment by calculating its cumulative infiltration coefficient, IC (%). The results showed a great difference in IC between dry and wet soil conditions. The IC for wet soil conditions was on average 24%, whereas it was 60% for dry conditions. Gullies with more than 50% surface vegetation cover exhibit the highest cumulative infiltration coefficients (81% for dry runs, and 34% for wet runs), but runoff transmission losses were not as clearly related to Correspondence to: A. Molina (molina vegetation cover as sediment storage as shown in Molina et al. (2009). The experimental field data of 16 experiments were used to calibrate a hydrological model developed by Fiener and Auerswald (2005) in order to simulate the transfer of concentrated flow along the gully beds. The calibrated
model was able to simulate the transfer of runoff water well, as the error on the simulated total outflow volumes is below 13% for 15 out of 16 cases. However, predicting infiltration amounts is difficult: the high sensitivity of model results to some crucial hydraulic parameters (runoff width, hydraulic conductivity and sorptivity) is one of the reasons why the relationships between model parameter values and gully features are relatively weak. The results obtained from the field experiments show that gully systems are key elements in the hydrological connectivity of degraded landscapes. The transfer of overland flow and sediment from the slopes towards the river system highly
depends on the presence/absence of vegetation in the gully
beds and should therefore be accounted for in assessments of
landscape degradation and/or recovery.
ISSN: 1027-5606
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Division of Geography & Tourism
× corresponding author
# (joint) last author

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