An erosion hazard index methodology (EHIM) for streams erodibility assessment (Ardabil-Province)

An erosion hazard index methodology (EHIM) was developed for assessing stream erosion. The index of stream erosion is designed as a management tool. Assessing stream erosion involves consideration of a range of aspects of streams and a value judgment about a desirable state. The assessment of the erosional indicators of streams was based on a state-wide assessment of physical stream condition. A scale from 0 to 100 was chosen as a basis for ranking where an erosion hazard index (EHI) of 100 indicates the very extensive possible erosion state and one of zero the stable or no erosion possible erosion state. In the EHIM five steps are necessary for calculation: to measure and select of basic and additional indicators, to calculate sub-EHIi for all selected indicators, to determine weighting factors for all selected indicators, to calculate a synthetic EHI using the sub- EHIi and weighting factors for all selected indicators and final step: to assess stream erosion based on synthetic EHI values. The EHIM was applied to a 378 number of Ardabil Province (NW of IRAN) for assessment and comparison purposes. Length of stream erosion (LE) was selected to serve as a basic indicator, while erosion susceptibility of lithology (LESi), length of streams with lateral erosion (LLAE), length of streams with bed erosion (LB), the plant cover and human impacts (LAHE), pasture lands (LPE) and their relationships and discharge of floods (Q2.33) were used as additional indicators. The results suggest that the EHIM is a valuable relatively uncomplicated methodology with simple principles, ease of calculation, reliable and intuitive results. As a practical planning tool, it can be widely used for the quantitative assessment and comparison of stream erosion states for a series of different streams or more complicated stream systems .However, planning for river management systems is complicated by a variety of uncertainties but this paper presents the evelopment of a simple assessment model for river management under uncertainty.