Resistance to Flow in a Cobble-Gravel Bed River with Irregular Vegetation Patches and Pool-Riffle Bedforms (Case study: Padena Marbor River)

This study was intended to estimate resistance to flow through velocity profile characteristics in a cobble-gravel bed river with 3D-Pool-Riffle bedforms and irregular distribution of flexible-submerged vegetation patches. To this end, a total of 39 velocity profiles consisting of four independent sections of Padena Marbor River have been studied. The finding showed that the depth of validity logarithmic law depends on the location of measurements including both inlet and outlet of the Pool. The predominant form of deviation from this law is frequently observed upwards at the inlet of the Pool and downwards at the outlet of the Pool and Riffle, which has a direct effect on the estimation of resistance to flow. Moreover, the results of resistance to flow revealed that the coefficients of resistance to flow are exponentially related to blockage area with a correlation coefficient greater than 0.8. Therefore, blockage area can be a suitable parameter in estimating resistance to flow in cobble-gravel bed rivers with 3D bedforms and irregular vegetations patches.