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Elahe Rahimi, Geological Survey of Iran (Islamic Republic of Iran)
Saeed Khodabakhsh, Bu-Ali Sina Universiy (Islamic Republic of Iran)
Mohsen Kalani, Geological Survey of Iran (Islamic Republic of Iran)
raziyeh Lak, Geological Survey of Iran (Islamic Republic of Iran)
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Human, opposite technological development, is unable against natural disaster events that cause irreparable damages. The reduction damages of this event in Nekariver catchment requires full recognition of Geology and other effective causes in flood appearing in Nekariver catchment that with associated crisis management ability, preparation and execution the comprehensive programs. The Nekariver rises in The Shahkuh Mtn. from Alborz in Gorgan and has a basin area of about 1922 km2. The analysis of the clast size indicates that there is a significant reduction in clast size in downstream. The sorting changes from very poorly sorted to moderately sorted from upstream to downstream and channel is filled with medium sand to pebbles in most upper parts. The source rock effect and changes in slope gradient are the most important factors influencing the variations of the sediments texture and river type. The fissure and fracturing features in the limestone units, laminate erosion and facilitate weathering of Gorgan schists to cause the parting and large fragmental rock movements that this fragmental rocks fragmentations because of mechanical erosion severely and the fragments to fall in slope elevations and river margins, also Marly limestone of Miocene Formations to product a large quantity mud and increases current density because of low resistance Miocene formation and high potential of sediments production and with other agents to increase destruction power of current and to threat residential regions and agriculture lands, also the most important factors on appearing events such as flood is lack of correct management programs about exploitation of resources such as irregular taking of gravel and sand, to fall down the bed river, irregular taking of forests and pastures by government and special companies.
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