Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Amal Kar ¹

Affiliations
1 Central Arid Zone Research Institute, Jodhpur, IN

Abstract

The present disorganised state of many streams in the Luni-Jawai plains of western Rajasthan has been attributed to a shift to an arid climate. The satellite images of the area, however, indicate a number of lineaments across the plains. Most cases of drainage disappearance appear related to these lineaments, as also the formation of river terraces and development of gullies. The findings tend to confirm at least two episodes of Quaternary tectonic movement in the area, resulting in channel changes/obliterations and other drainage anomalies. The pattern of drainage disorganisation suggests that change of climate could at best be an associated factor, and not the primary one.

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Amal Kar ¹

Affiliations
1 Central Arid Zone Research Institute, Jodhpur 342003, IN

Abstract

Most of the studies on the Quaternary landform evolution in the Thar are devoted to broad morphological processes, the changing climate and absolute daring of different episodes of sedimentation. Reconstruction of actual sequence of events which led to the development of many present day forms and the role of neotectonism have received relatively less attention. The author, during his traverses in the desert, came across certain evidences to suggest that a knowledge of present day process - form interactions may provide significant clues to the possible past processes. A few examples have been cited.

Keywords

Geomorphology, Quaternary Landform, Thar Desert, Rajasthan.

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P. C. Moharana ¹, Amal Kar ¹

Affiliations
1 Division of Natural Resources and Environment, Central Arid Zone Research Institute, Jodhpur – 342 003, IN

Abstract

A quantitative study on fluvial processes was carried out in an upland stream catchment (9.3 ha) near Agolai in the NE of Jodhpur district in the Thar Desert in Rajasthan. The catchment of the studied second order ephemeral channel (1.0 - 1.4 km long and 1.0 - 1.5 m deep) has developed on a hill - rocky/gravelly pediment - colluvial plain sequence on rhyolite. Initial results of measurements of channel parameters during two significant runoff generating events of 42 mm and 52 mm in 2007 showed peak discharges of 20 m³s^-1 (upstream) and 13 m³s^-1 (downstream) that moved sediments (bedload) to distances of 43 m - 141 m in the upstream reach, 6-28 m in the middle reach and 63-95 m in the lower reach. The long profile and cross profile measurements showed a balance between load and discharge through a sequence of alternate deposition and erosion throughout the channel. Hypsometry curves revealed maximum erosion (7.7 cm) in the upper reach and aggradation (2.90 cm) in the lower reach. Cross profile measurements showed bank cuts (6 cm) and vertical incisions (1-2 cm) on the rocky-gravelly V shaped valley in the upper reach, incision (4- 30 cm) and localized higher deposition (10-12 cm) in the narrow (<1m) and deep (>1m) U shaped valleys in middle reach and mainly deposition (13 cm) on the wide (1-4 m) and shallow channels (0.1 to 0.2 m) in the lower reach.

Keywords

Arid Catchment, Channel Morphology, Erosion, Hypsometry, Particle Movement, Ephemeral Flow, Monitoring, Thar Desert, Rajasthan.

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Amal Kar ¹

Affiliations
1 Jodhpur, IN

Abstract

No Abstract.

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