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| Titel |
Assessing the reduction of the hydrological connectivity of gully systems through vegetation restoration: field experiments and numerical modelling |
| VerfasserIn |
A. Molina, G. Govers, A. Putte, J. Poesen, V. Vanacker |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 13, no. 10 ; Nr. 13, no. 10 (2009-10-12), S.1823-1836 |
| Datensatznummer |
250012020
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| Publikation (Nr.) |
 copernicus.org/hess-13-1823-2009.pdf |
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| Zusammenfassung |
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 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. |
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