sadat Feiz Nia; Mariam Musavian; Zohreh Abdolahian Dehkordi; Khadijeh Ebrahimi Dorche
Physical characteristics of drainage basins suchas geological materials, landuse type and vegetation cover, soil type, surfacepermeability, depth of underground water table, topographical conditions anddrainage are important factors in flood occurrence which affect prevailingequations on water movement ...
Physical characteristics of drainage basins suchas geological materials, landuse type and vegetation cover, soil type, surfacepermeability, depth of underground water table, topographical conditions anddrainage are important factors in flood occurrence which affect prevailingequations on water movement in drainage and determine storage capacity ofdrainage basins. Geology is one of the most important factors affecting floodoccurrence of drainage basin. In this study it is attempted to investigate theeffect of geology factor on flood occurrence in Joneghan drainage basin,Shahr-e – Koord, using a new method. In this respect, after preparing base mapsconsisting of slope amount , geology , landuse , erodibility of geologicalmaterial , soil depth and drainage pattern , studies were performed in twostages as follows: In the first stage, flood occurrence of hill slopes of eachsub- catchment was investigated. For doing so, work unit map was prepared usingslope and infiltration maps. Then in each sub-catchment, land use, erodibilityof geological materials and soil depth were overlaid with work unit map one byone and dually. In the second stage, flood occurrence of drainage wasinvestigated as follows: First, longitudinal profile of main drainage of eachsubcatchment was prepared using GIS. For investigation of flood occurrence ofdrainages, slope and permeability of geological units were used. The results ofthe first stage showed that permeability, slope, erodibility of geologicalmaterials and soil depth have the greatest effect on flood occurrence,respectively. Also based on this four – factor method, subcatchments weredivided into five flood occurrence classes as follow: low, low to medium,medium, relatively high, and high. The results of the second stage showed thatdrainage flood occurrence belongs to two classes of low to medium and medium.By combining slope and drainage flood occurrence, it can be concluded that thethird subcatchment with medium flood occurrence is more susceptible to floodrelative to other subcatchments. With regard to the results of the presentstudy, it can be concluded that geology has high impact on flood occurrence andpermeability of geological materials decrease flood occurrence in the basin.