Channel-forming discharge and river meander migration modeling of the Pilcomayo River in the area of Misión La Paz (Argentina) and Pozo Hondo (Paraguay)

Bankfull discharge effective discharge meander migration

Lacunza, Esteban ; Garcia ; Marcelo H.

关键词: Bankfull discharge effective discharge meander migration;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/95438/LACUNZA-THESIS-2016.pdf?sequence=1&isAllowed=y

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来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The Pilcomayo River shows high planform mobility in the area of Misión La Paz (Argentina) - Pozo Hondo (Paraguay) that is associated with the river's bed material and the hydrologic regime of the stream. In order to better understand the river's morphodynamics, RVR Meander, a 2D depth-averaged analytical model, was used to assess the channel's planform evolution in time. The model uses a single discharge value for the simulations, thus estimation of a channel-forming discharge was necessary for the model application. Of the available methodologies for determining the channel-forming discharge, two are described herein, namely: the bankfull discharge and the effective discharge. The bankfull discharge was obtained with the stage-discharge rating curve after identifying the stage corresponding to the elevation of the active floodplain. The effective discharge was obtained from available data of flow and suspended sediment loads.The results present discrepancy with the bankfull having return periods between 4 and 7 years whereas the effective discharge has 1.01\yrs of recurrence interval. Further analysis of the bankfull stage conditions are recommended. The RVR Meander results are compared with river centerline planform variations obtained from LANDSAT imagery for the period between 1987 and 2015. RVR Meander estimations of river mobility were remarkably lower than what the image analysis showed. River channel displacement seems to be caused by the recovery of old meander scars or the occurrence of cutoffs as opposed to bank erosion alone.