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http://krishi.icar.gov.in/jspui/handle/123456789/62023| Title: | Quantitative Measurement of Arid Fluvial Processes: Results from an Upland Catchment in Thar Desert |
| Other Titles: | Not Available |
| Authors: | P.C.Moharana Amal Kar |
| ICAR Data Use Licennce: | http://krishi.icar.gov.in/PDF/ICAR_Data_Use_Licence.pdf |
| Author's Affiliated institute: | ICAR::Central Arid Zone Research Institute |
| Published/ Complete Date: | 2010-07-01 |
| Project Code: | CAZRI/T01/27 |
| Keywords: | Arid catchment Channel morphology Erosion Hypsometry Particle movement Ephemeral flow Monitoring Thar Desert Rajasthan |
| Publisher: | Journal Geological Society of India |
| Citation: | Not Available |
| Series/Report no.: | Not Available; |
| Abstract/Description: | 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) 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. |
| 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. |
| ISSN: | Not Available |
| Type(s) of content: | Research Paper |
| Sponsors: | Not Available |
| Language: | English |
| Name of Journal: | Journal Geological Society of India |
| Journal Type: | Research |
| NAAS Rating: | Not Available |
| Volume No.: | 76 |
| Page Number: | 86-92 |
| Name of the Division/Regional Station: | Division of Natural Resources |
| URI: | http://krishi.icar.gov.in/jspui/handle/123456789/62023 |
| Appears in Collections: | NRM-CAZRI-Publication |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| pcm-akar-erosion process-paper.pdf | 372.08 kB | Adobe PDF | View/Open |
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