Determining the amount of sediment deposited behind dry wall and wire cage sills for the gully rehabilitation in a sub-watershed of the Coruh river basin including Oltu, Olur and Yusufeli

This study was carried out in Yusufeli, Oltu and Olur sub-watershed, which were evaluated within the scope of Coruh River Basin Rehabilitation Project. The aim of the study is to reveal the potential effects of gully rehabilitation on sediment control and capture by measuring how much sediment and litter is retained by these dry walls and wire cage sills. In the study, firstly, sample gully channels of each sub-watershed were selected. The number of sills, sill top length, post length and sediment occupancy rates of dry wall and wire cages on these selected areas, namely gully streams, were measured. Afterwards, the soil samples taken from these sills and the total amount of sediments were calculated. As a result, the average sediment occupancy rate of the drywall and wire cage sills installed into gully channels was determined as 67%. This value was measured as 58% for Olur, 67% for Yusufeli and 76% for Oltu sub-watershed. Based on the current sediment occupancy rates, the total sediment amounts were calculated as 4220 tons for Oltu, 9256 tons for Olur and 11488 tons for Yusufeli sub-watershed. The deposited unit sediment amounts (ton/m) behind the sills (amounts of sediment accumulated behind a 1 m dry wall and/or wire cage sills) measured as 0.50 for Olur, 0.59 for Yusufeli and 1.35 ton/m for Oltu sub-watershed. In this context, Oltu sub-watershed with the highest sediment accumulation showed a significant difference compared to other sub-watershed (p < 0.05).