A deposit model does not merely specify physiographic setting, but encompasses the entire history of the deposit from alluvial deposition to erosion and current state of preservation. Features such as stratigraphy, particle size, sorting and weathering have a strong influence on aggregate quality. Alluvial fan deposits are poorly sorted and lower in aggregate quality than well-sorted river terrace and floodplain deposits.
Size varies with physiographic setting and preservation.
For example, dissected high terraces tend to be too small to provide sufficient tonnages to support aggregate mining. 4-Environmental effects of mining. Mining impacts vary from minor excavations for fill material in fans and dissected terraces to sustained operations that produce large pits and require facilities for processing and delivery of aggregate. Pits on floodplains require de-watering of the deposit and can lower the local water table. Small excavations on uplands can be reclaimed to native vegetation or rangeland.