Record Details

Quantitative Measurement of Arid Fluvial Processes: Results from an Upland Catchment in Thar Desert

KRISHI: Publication and Data Inventory Repository

View Archive Info
 
 
Field Value
 
Title Quantitative Measurement of Arid Fluvial Processes: Results from an Upland Catchment in Thar Desert
Not Available
 
Creator P.C.Moharana
Amal Kar
 
Subject Arid catchment
Channel morphology
Erosion
Hypsometry
Particle movement
Ephemeral flow
Monitoring
Thar Desert
Rajasthan
 
Description The results of our experiment are based on field observations during two effective rainfall events in the
desert. It was found that the apparently low rainfall of desert sometimes causes significant runoffs that can
influence channel morphology and sediment movement. At the same time, channel dimensions have also been found to influence the erosion pattern at several locations. Unlike, the sequential pattern of erosion and
depositions in channels in humid channels, here, there has been alternate erosion and depositional activities. This is due to characteristics influence of short duration rainstorms in arid zone, duration and velocity of runoffs
and their ability to erode/deposit the sediments. While scouring has remained the dominant erosion process in
the upper and in a section of lower part of the channel, the middle and the extreme end of the channel have favoured depositions. Due to such erosion/depositional activities as well as change in channel slope, runoff velocities have been either high or low causing more/less movement of particle. Relationship between particle shape (flatness) and their movement showed that flatness influenced particles in all the sections of channel. In the lower part even more flat particles moved greater distances because those were lighter in weight. Though these observations are based on field measurements, definite conclusions would depend
upon the number of traceable particles and the number of observations. The spatial relationship between
discharge and erosion/deposition has been good; however, the conventional relationship between velocity-runoff discharge is yet to be established at each section of the channel which needs a much larger data set. Despite thisour preliminary results provide some field level information on process-form interactions along gravel – bed upland ephemeral channels in the monsoon – driven Thar desert that will help to further understand the process and monitor the situation.
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 ephemeralchannel (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 generatingevents 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 63-95m 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 showedbank 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) 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.
Not Available
 
Date 2021-09-14T11:19:31Z
2021-09-14T11:19:31Z
2010-07-01
 
Type Research Paper
 
Identifier Not Available
Not Available
http://krishi.icar.gov.in/jspui/handle/123456789/62023
 
Language English
 
Relation Not Available;
 
Publisher Journal Geological Society of India