Groin type and vegetation in groin fields directly affect flow field, bank protection, and river evolution. Many studies focus on fixed-bed contexts, but there are few studies on the influence of riverbed changes on hydrodynamic characteristics around groins. In this study, three types of groins are investigated experimentally in fixed and mobile beds in terms of time-averaged flow characteristics, turbulence characteristics, and bed changes. In both fixed- and mobile-bed experiments, vegetation reduced erosion of the groin field and main stream. Compared with the fixed-bed experiment, the velocity in the main stream was decreased in the mobile-bed experiment, and the longitudinal turbulence intensity and lateral momentum exchange were increased. In this study, an improved three-dimensional groin group (upstream wing submerged T-shaped groin group) produced a lower sediment scouring capacity, average scour depth, and entrainment coefficient k than I-shaped and T-shaped groin groups.

Three years of hourly COD and NH₄⁺-N measurements for two full-scale integrated constructed wetlands (CWs) treating secondary effluents from sewage treatment plants (STPs) were used to quantify the proper sampling frequency (SF). The modified coefficient of variation (CV_m) and average variation rate (VR_a) were calculated to monitor the dynamics and annual average performance, respectively. It was found that (1) under CV_m 5%, VR_a 5%, and VR_m 5%, the sampling intervals (SI) of COD can be set as 1.19 h, 526.5 h, and 110.1 h, respectively, and the SI of NH₄⁺-N should be 4.51 h, 66.3 h, and 26.8 h, respectively; (2) under CV_m 10%, VR_a 10%, and VR_m 10%, the monitoring intervals of COD can be set as 11.92 h, 1401.7 h, and 233.5 h, respectively, and the monitoring intervals of NH₄⁺-N should be 30.73 h, 139.3 h, and 50.5 h, respectively. Therefore, to meet the need of monitoring the dynamic changes in data, hourly and 4 h SIs were recommended for COD and NH₄⁺-N evaluation, respectively, when it is necessary to consider the operation and maintenance costs at the same time, 11 h and 30 h SIs were proper for COD and NH₄⁺-N evaluation, respectively. The methods proposed in this study could provide reference to improve the management and evaluation level of full-scale CWs.