Diverse bed forms are observed in river bank. Occurrence of pools and riffles are due to the discontinuity over flow cross section and banks in straight rivers and natural channels. Aquatics spend various stages of growth in different parts of bed forms including riffles (shallow) and pools (deep). This causes changes in water quality by regulating the amount of oxygen. From the standpoint of the hydraulic, the roughness increases because of the variations of flow depth and flow cross section in pools and riffles, thereby it causes energy losses and local erosion. Vegetated walls have significant effect on sustainability and flow resistance, in addition, these walls increase roughness coefficient in walls and flood plain. Due to adjustment of environmental conditions and energy loss caused by vegetated wall and bed forms, their interaction is of vital importance in river improvement projects. Consequently it is necessary to investigate the impact of bed form, flow, and vegetation on the stability and fluvial processes in more detail. The objective of present study is to investigate the effect of successive pools and riffles and its interaction with vegetation wall in turbulent flow characteristics. Present study was conducted in two set in hydraulic laboratory of Agriculture College at Isfahan University of Technology. In the first set, the experiments were conducted in a flume of 16 m long, 0.9 m wide, and 0.6 m deep whereas the second set of experiments were performed in a laboratory flume with 8 m long, 0.4 m wide, and 0.6 m deep with rectangular cross section. Also, another set of experiment were carried out over an interval of 100 m long of Plasjan river located in Chadegan, Isfahan. The flow velocity was measured by 3D Acoustic Doppler Velocimeter (ADV). Velocity data was filtered by WinADV software and results were analyzed based on favorable data of velocity profile, Reynolds stress and turbulence intensity. Also by use of quadrant analysis the distribution of the stress tensor and its symptoms were analyzed in different parts of the flow. In laboratory studies, the channel bed form was covered by gravel with a median diameter of 10 mm and the flume wall was covered by straw stem as vegetation. The experiments were carried out for two crest slopes 5 and 20 degrees for input and output respectively, two aspect ratios and five ltr" Key words: Pool-Riffle bed form, straw stem as vegetation, Turbulence flow, Flow structure, Quadrant analysis
