تاثير عوامل زمين شناسي در تغيير مسير رودخانه ي هيرمند و نقش تاريخي آن در جابجايي سكونتگاه در سيستان

The Effects of Geology in Hirmand River Direction and Its Historical Role in Habitations Transposition in Sistan

the Hirmand river is a vital lifeline ofʹ Sistan which Sistanʹs lire completely depends on continuation flow of Hirmand river. Herodotus byword if "E gypt is as Nile river giff accept Sistanʹs field civilization owe to Hirmand river. Thhis river had veered its direction as satellite illustrations prove. Also historical resources has been mentioned these veered directions of hinnand invite by destroying cities, villages and sometime the whole previous civilizations. Thus this river is influential on destroying civilization like shaping, growing and developing civilization in this district. This present research is mentioned to various reasons of geology in eluded simplicity of erosive and precipitation which are related to texture and soil nature of the field, tectonic factors which had made Hirmand change directions through the history and spatial effect of the earth. The conclusion of this research shows that erosive factors are more noticeable than the others, because existence of levels and sandy-grit with fine aggregate, less viscosity and erosive between clay line aggregate of alternation layers and silty surface layers. However one of the efficacious agents in erosion simplification and movements of Hirmand river is divergence of soil beside fold growth in stone- foundation. Besides these factors the role of severe winds in this area and human activities arc completely clear.