|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
,3
1 Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel
2 Department of Geography, Hebrew University of Jerusalem, Jerusalem 91905, Israel
3 Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel, and Department of Geography, Hebrew University of Jerusalem, Jerusalem 91905, Israel
Intense rainstorms cause debris flows on escarpments in hyperarid environments. In contrast with more temperate environments, there have been no direct observations on rainfall intensities and durations required for initiating debris flows in hyperarid environments. Here, we report rainfall volume and intensities, acquired by gauge and radar measurements, for two successive storms along the hyperarid (<50 mm/yr) western escarpment of the Dead Sea basin. These rainfall data were analyzed in conjunction with detailed mapping of debris flows that occurred during these storms to determine values of rainfall intensity and duration required to generate debris flows on the Dead Sea western escarpment.
The first of the two analyzed storms occurred on 2 November 1995. During this storm, two convective cells rained sequentially within a 5 h period at the lower reaches of the Nahal David and the Nahal ‘Arugot that dissects the western escarpment of the Dead Sea, Israel. This storm triggered debris flows in 38 small (<3 km2) and high-gradient drainage basins along the escarpment. Total rainfall volume and spatial distribution were determined by 10 cumulative rain gauges that were also used to calibrate rainfall-intensity distributions from radar data. For this storm, region, and landscape, rainfall intensities exceeding 30 mm/h for a duration of 1 h were required to initiate debris flows.
A second storm in the same area on 17– 18 October 1997 allowed the evaluation of the results determined from the 1995 storm. In this second, more regional storm, maximum rainfall intensities were 19–27 mm/h for a duration of 45 min. These values, lower than the 30 mm/h minimal threshold defined in the previous storm, are consistent with the occurrence of only three debris flows. The small number of debris flows resulted from the concentration of the highest intensities of rainfall on the desert plateau and not directly on top of the canyon walls.
Most first- to third-order basins draining the Dead Sea escarpment contain evidence of zero to three late Holocene (<3000 yr) debris flows. From analysis of the two storms, we propose that most of these debris flows were triggered by storms similar to the 2 November 1995 event in which localized convective cells had rainfall intensities of >30 mm/h and durations of at least 1 h. The small number of debris flows that has occurred during the late Holocene indicates that such events are rare at the scale of individual drainage basins.
Key Words: debris flows • Dead Sea • escarpment • extreme storms • arid environment • floods
This article has been cited by other articles:
|
|
 |
|
  J. W. Bell and P. K. House Did Plinian eruptions in California lead to debris flows in Nevada? An intriguing stratigraphic connection Geology, March 1, 2007; 35(3): 219 - 222. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. E. Bullard Arid geomorphology Progress in Physical Geography, August 1, 2006; 30(4): 542 - 552. [PDF]
|
|
|
|
 |
|
 U. Dayan and E. Morin Flash flood-producing rainstorms over the Dead Sea: A review Geological Society of America Special Papers, January 1, 2006; 401(0): 53 - 62. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Greenbaum, A. Ben-Zvi, I. Haviv, and Y. Enzel The hydrology and paleohydrology of the Dead Sea tributaries Geological Society of America Special Papers, January 1, 2006; 401(0): 63 - 93. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Bartov, R. Bookman, and Y. Enzel Current depositional environments at the Dead Sea margins as indicators of past lake levels Geological Society of America Special Papers, January 1, 2006; 401(0): 127 - 140. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. J. Hartley, A. E. Mather, E. Jolley, and P. Turner Climatic controls on alluvial-fan activity, Coastal Cordillera, northern Chile Geological Society, London, Special Publications, January 1, 2005; 251(1): 95 - 116. [Abstract] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
