Abstract
Water erosion is an important erosion type that erodes and transports the most. With the effects of stream water, both streambank and gully erosions cause even more soil transport and debris accumulation resulting more flood events and associated loss of life and properties, as well as increasing the deposition of sediment in dam reservoirs that shorten the economic lifespan of these dams. This study was carried out in 14 different bank erosion sites (stream reach) in the Oltu Micro Catchment (OMC), one of the sub-watershed of the Coruh River Basin, to measure gully and streambank erosions over five-year long study period using “erosion pin method”. Oltu Micro Catchment has arid and semi-arid climate and has a 37% slope degree with a rugged structure. Over the five-year study period, the annual gully and streambank erosion rates were ranged from 1.25 to 8.79 cm/yr and the five-year average was measured as 4.43 cm/yr. The five-year soil losses were ranged from 30.5 to 190.8 tons/km/yr, and the five-year average was measured as 83.9 tons/km/yr. Compared to 1st and 2nd order streams, most of these measured soil losses were due to gully erosion (78%). In addition, it was determined that very large increase in bank erosion was occurred due to increase in rainfall in this semi-arid region showing that these types of watersheds are sensitive to bank erosions. As a conclusion, streambank and gully erosions are dynamic processes effected by the spatial and temporal scale differences under varying climate settings. Additionally, this study is a pioneer one in the region that identifies a need for the conservation practices (particularly for the gullies) to reduce the soil losses and deposited sediment in the whole channel system and eventually in dam reservoirs.
Highlights
Toprak; ekolojik, ekonomik, biyolojik ve kültürel fonksiyonları ile bitki, hayvan ve en önemlisi insanlar için çok önemli doğal ve aynı zamanda tükenebilir bir kaynaktır
well as increasing the deposition of sediment in dam reservoirs that shorten the economic lifespan of these dams
the five-year average was measured as 4.43 cm
Summary
Çoruh Nehri Havzası ülkemizin kuzeydoğusunda yer alan toplamda 466 km uzunluğundaki Çoruh Nehri’nin drenaj havzasıdır. Bu havza Türkiye yüz ölçümünün %2,5’ine, bu da yaklaşık 2 milyon hektara karşılık gelmekte olup Bayburt, Erzurum ve Artvin illerinin büyük bir kısmını kapsamaktadır (Şekil 1). Havzanın yıllık yağış ortalaması 560 mm olup, genel olarak dağlık bir yapıda ve üzerinde 2500 ve 3000 m üstünde birçok dağ ve dağ silsilesine ev sahipliği yapmaktadır. Bu çalışmanın gerçekleştirildiği OMH’sı, Çoruh Nehri Havzası’nın güneydoğusunda yer alan toplamda 36900 hektarlık bir alanı kapsamaktadır (Şekil 1). Havzanın yükseltisi 1170 m ile 3047 m arasında değişmektedir. Oltu MH’sı arazi kullanım şekli bakımından, 6275 hektarı bozuk orman, 3866 hektarı verimli orman, 17235 hektarı mera ve 6265 hektarı yerleşim yeri ve diğer alanları kapsamaktadır. Havzanın düşük rakımlı vadi düzlüklerinde verimli tarım alanları görülmektedir (Duman, 2017)
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