Preliminary Analysis of the Effect of Worked Wood Piles in Straight Channels

Eco-friendly low-head structures such as blunt nosed chevrons, wood bundles, worked wood piles etc. provide an effective solution to ensure grade and sediment load control in rivers, as well as to introduce morphological variations in the channel bed promoting biodiversity. Worked wood piles are usually installed near the outer bank in order to redirect the flow away from it, thus stabilizing the basin. Moreover, these structures increase the natural organic content in channels and create pronounced scour and dune features in their vicinity, giving shelter to a host of aquatic organisms and fish species. However, till date, a comprehensive analysis of the scour features occurring in the presence of worked wood piles is absent in literature. To shed light on this underexplored topic, the present study provides some initial results on the equilibrium and temporal scour characteristics in the vicinity of worked wood piles. Experiments were conducted with such structures in straight channels under a wide range of hydraulic conditions. Isolated structures as well as series of two structures were tested. Among others, the equilibrium scour morphology due to worked wood piles resulted to be considerably influenced by inflow conditions, tailwater level and number of structures in case of series arrangement. Namely, the scour and dune features in the stilling basin of the structure are more enhanced for higher discharge and tailwater and in case of two worked wood piles in series. Moreover, the development of scour and dune geometry was recorded at regular intervals of time for the entire test duration which revealed that the rate of increase of scour area in case of two worked wood piles in series is higher in specific intervals during the test depending on the hydraulic conditions. Overall, the results offer important observations and a preliminary analysis of the local scour phenomena around worked wood piles, aiming at providing a basis for future design guidelines