Sediment Transport Measurement in the Koshi River: Comparison Between Historic and Recent Measurement Results Article Swipe
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· 2019
· Open Access
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· DOI: https://doi.org/10.11648/j.ajwse.20190503.12
· OA: W2979798859
This study presents the results of sediment transport measurement in the Koshi River with a comparison between historic and recent measurement techniques. Based on the historic sediment measurement data for the period 1948-1981, the yearly sediment load at Barakhshetra varied between 49 and 283 million m<sup>3</sup>, with an average of 95 million m<sup>3</sup>. The coarse, medium and fine fraction contribute by respectively 19, 25 and 56% to the total sediment load of the Koshi River. The average total yearly sediment load at Chatra was estimated as 130 million m<sup>3</sup>, of which about 60 million m<sup>3</sup> is bed material load which contributes to the aggradation on the alluvial fan. This historic data relate to measurements with depth-averaged sampler form cableways. Recent practices collect surface sediment samples from the riverbank to estimate the sediment transport in the river, which include the JPO-SKSKI and DHM sediment samples. The average yearly sediment load at Chatara on the basis JPO-SKSKI and DHM measurement correspond to 44.5 million m<sup>3</sup> and 57 million m<sup>3</sup> respectively. Moreover, a comparison between the percentages coarse, medium and fine sediment for the historical measurements (EDI method) and JPO-SKSKI and DHM measurements (surface sampling near the bank) concluded that sampling from the bank results in a serious underestimation of the contribution of the coarse sediment to the total sediment load of the river.
