Field Study of Three–Parameter Flow Resistance Model in Rivers with Vegetation Patch

Bed shear stress in coarse–bed rivers with vegetation patches is one of the challenging parameters hydraulic engineering, mechanical fluvial morphology, and environmental studies. Based on this necessity, study, values bed four reaches Iran were estimated compared using methods boundary layer characteristics, logarithmic law, Darcy–Weisbach. Data collection study started February 2021 ended April 2021. Estimation flow resistance a key factor many numerical physical models. In order to obtain reasonable evaluation factor, it necessary measure calculate variables flow. Accordingly, experimental design includes surveying operations, velocity measurement, sampling sediments. The results show that due forms, patches, variations depth grain size river, universal distribution law (the log law) may not be suitable estimate velocity, which parameter resistance. This calls for more justifiable are affected by near–the–bed conditions. three–parameter model presented, shows an average error 17%, indicating accuracy model. investigation 71 measured profiles occurrence Dip phenomenon near patches. However, moving away from effect decreased, illustrate S–shaped distribution. relative differences between Darcy–Weisbach characteristics method (BLCM) equal 87% 39%, respectively, agreement method. application theory BLCM. simplify data field, suggested.