Estimating the Lateral and Bed Erosion of Gully by Dendrogeomorphological Analysis of Tree Roots in Nilkooh Catchment (Galikesh), Golestan Province

Dendrogeomorphology is one of the most important techniques for determining the age of geomorphological processes such as slope movements, flooding, erosion, earthquakes and other processes. One advantage of application of dendrogeomorphology in the estimation of gully erosion is that it can estimate the annual rates of erosion. The aim of this research is to estimate the lateral and bed erosion of gully by dendrogeomorphological analysis of tree roots in Nilkooh catchment. To achieve this goal, a total of 50 samples from the roots of broadleaf trees, including Evangelical, wild persimmons, alder, oak, hornbeam, hawthorn and maple that have been exposed after erosion, were dated. The 35 samples were tested for lateral erosion of gully and 15 samples were also examined for gully bed erosion. During sampling, the information such as slope gradient, distance of the sample from the wall of gully and geographical coordinates were also recorded. Samples were dried in natural conditions and have been sanded for better clarity. In this study, exposed roots were sampled during 2013-2014. The minimum and maximum ages of roots were 3 and 14 years, respectively. The study reveals that the average rate of lateral and bed erosion of gully are 0.053 and 0.107 meter, respectively. The lateral erosion of gully has inverse correlation with elevation and gradient, whereas bed erosion of gully has positive correlation with elevation gradient.