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| Titel |
The Effects of Wind Driven Rain Vectors on the Stream Power of Thin Flow |
| VerfasserIn |
H. Samray, G. Erpul, D. Gabriels, W. M. Cornelis |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065511
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| Zusammenfassung |
| Stream power of a thin flow is generally explained as a function of runoff and slope
under wind-free rainfall conditions, and the effect of vertically impinging raindrops
on flow is always considered as a resistance to its downward movement. On the
other hand, the raindrop and flow interactions for interrill erosion with wind-driven
rain (WDR) differ at the impact-flow boundary. Since WDR fall trajectory varies
with differences in horizontal wind velocity, both magnitude of raindrop normal
and lateral stresses on flow change and a vector field is established, resulting in
differentially directed lateral jets of raindrop splashes with respect to downward
flows occur. Therefore, to account for these differences, a vector approach with the
kinetic energy fluxes or the stream powers of raindrop splashes and flow is required
instead of vector-free parameters of rainfall intensity and interrill runoff. WDR
experiments were conducted to evaluate the changes in the resultant stream power
(Ωr, J m-2 s-1) with the raindrop impact velocity vector with a two-dimensional
experimental set-up in a wind tunnel. Synchronized wind and rain simulations - the
rains were accompanied by the horizontal wind velocities of 0, 6, 10, 12 ms-1
- were applied to the test surfaces on windward and leeward slopes of 2, 3, 4 5,
7, 9, 11Ë . By this way, the diverse WDR fall trajectories with the angle of rain
incidences (Φo) between the wind vector and the plane of the test surface were obtained
by changing slope aspect from windward to leeward. The rainfall intensity was
directly measured with 20 small collectors placed over a 20 x 200 cm test pan on
the inclined planes before the runs and the runoff discharges were taken every 5
min interval during 60 min WDR simulations. The results showed that the normal
energy flux of WDR (Ω(drop)n, J m-2 s-1) was as much as 45.4 times more in
the windward slope than that of the leeward although the along-surface energy
flux of WDR (Ω(drop)s) did not change that much as Ω(drop)n did with the aspect
and the value was 7.7. Whereas, the considerable differences occurred in Ωr with
the slope aspect and the ratio as large as 259.4 was attained with the rains driven
by the wind velocity of 12 ms-1 and incident on the sloping test surface of 11Ë .
This fact indicated that the thin flow hydraulics varied significantly with the slope
aspects under WDR and could bring about substantially different sediment delivery
rates.
Key words: stream power, WDR vectors, thin flow, lateral jets, angle of incidence |
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