Sand depositiion in valley regions are mainly due to erosion on the catchment areas. Due to rapid infrastructural developmental activities in hilly areas, surface cover is removed and sub surface get exposed. Heavy rains carry down these loose mass along the natural water ways such as rivers, etc. The additional load of loose mass gradually gets deposited in the river bed and carrying capacity of the natural river systems gets constricted. So, the load gets inflated and breach the river bunds. Impact of the tremendous kinetic energy wash away colloidal materials but heaver fraction of soil i.e. Sand and silt remains near the mouth of the breach portion. These sand and silt thus gets deposited in fertile agricultural land rendering it unsuitable for cultivation. The depth of deposition may very from ten centimeter to even up to two meter. One of the most daring example is in Assam, India where thirty two thousand hectares of fertile cultivable land was degraded due to sand depositional problems. If any technology is available world wide for reclamation of such land, we are interested to proceed.
Sand deposition is just another name for soil erosion. The soil gets eroded due to deforestation and torrential rains. This soil then gets deposited somewhere else, be it a sea bed or another piece of land. In some cases, sand deposition is beneficial as the soil may contain of nutrients that are required for good growth of vegetation.