T210 Advances in Arid Lands Geomorphology

Tuesday, 24 September 2024
1:30 PM - 5:30 PM
210B

THE IMPACT OF EXTREME RAINSTORMS ON ESCARPMENT MORPHOLOGY IN ARID AREAS: INSIGHTS FROM THE CENTRAL NEGEV DESERT

Paper number: T210-10
Program: Technical Sessions
Time: 4:00 PM – 4:15 PM

Authors

Abstract

The impact of climate on topography was previously demonstrated at mountain range scales and under pronounced gradients in average climatic properties such as mean annual precipitation or temperature. However, in arid areas, where both meteorological observations and rainfall measurements are scarce, and erosive events are rare and discontinuous in space, the determination of climate properties that govern surface processes is challenging. Here, we attempted to bridge this gap by documenting systematic variations in climatic properties along a 40 km arid escarpment in the central Negev desert (Israel) and their associated topographic signature. We used LiDAR-derived topographic data coupled with field measurements to characterize the morphology of cliffs and slopes. Sub-hourly rainfall intensity record from a convection-permitting numerical weather model used for novel storm-scale rainfall statistical analysis. At last, we conducted grid-based hydrological simulations of synthetic rainstorms, revealing the frequency of sediment mobilization along the sub-cliff slopes.

Our results indicate that the mean annual rainfall along the escarpment decreases from ~90 mm in the southwestern (SW) side to ~45 mm in the northeastern (NE) side. Toward the drier NE side, topographic cliff gradients and the percentage of exposed bedrock over the cliffs increase. Also, sub-cliff slopes in the NE side are systematically straighter, shorter, and associated with a smaller sediments relative to the wetter (SW) side. Storm-scale statistical analysis reveals a trend of increasing extreme (>10 years return-period) intensities toward the northeastern side, opposite to the trend in mean annual rainfall. Hydrological simulations based on these statistics indicate a higher frequency of sediment mobilization in the northeast, which can explain the pronounced topographic differences between the sides. Our results indicate that significant morphologic differences across a relatively short distance (<50 km) can be imprinted in arid landforms due to spatial gradients in storm-scale properties and highlight the sensitivity of arid landforms to extreme events.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-403742

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