عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Introduction: Since long ago, controlling the floods and artificial groundwater table`s recharge have been one of the most important aims of performing floodwater spreading systems in arid and semi-arid regions. On the other hand, determining appropriate locations to perform the floodwater spreading systems based on various indices is of utmost importance. However, determining appropriate locations for performing floodwater spreading plans using traditional methods was very difficult that caused complex problems in this regard. Therefore, geographic information system as well as its techniques is able to integrate various information layers into different models and they can be used in floodwater spreading due to their short-time consumption and high accuracy in locating appropriate areas. One of the mentioned problems can be related to the southern plains of Ilam Province; since it is not only encountered with the shortage of surface and groundwater resources, but also the occurrence of destructive floods. Considering the fact that it is not possible to use watershed management methods in upper flood plains of the studied areas, the best method for controlling floods and using surface currents is performing floodwater spreading projects. Thus, the current study investigated the effective factors in locating areas susceptible to floodwater spreading in southern plains of Ilam Province using Multi Class Map model through a geographic information system.
Methods: This study has utilized 1:50000 and 1:250000 topographic maps of National Geography Organization of Iran, geological land use and capability maps, the province`s political subdivisions, satellite images from Landsat 8 sensing OLI of 2013 as well as ILWIS, version 3.3, software.
In this study, five parameters of quaternary units, slope percentage, alluvium thickness, land capability and land use were investigated as the affective factors in locating areas susceptible to floodwater spreading as well as artificial recharge in southern plains of Ilam Province using Multi Class Map as stated below.
Preparation of geological mass layers (alluvium units, Bakhtiari, Aghajari and other structures), slope layer (with 0-2, 2-5 and more than 8 classes), alluvium thickness layer (a thickness of less than 20, 20-40, 40-70 and more than 70 m), land capability layer (alluvial flood plains, hill-sided plains, plateau, mountain and hill).
Integration of prepared mass layers and creating primary layers for areas susceptible to floodwater spreading: Prepared information layers were integrated using Raster Calculator function and the studied area was zoned regarding areas susceptible to floodwater spreading.
Preparing land use map: In this research, utilizing land use was actually considered as the limiting layer for floodwater spreading areas. By limiting layer, those areas are intended that despite having best susceptible circumstances for establishing floodwater spreading systems, they can be used for administrating the system, for example, agricultural lands, forest areas and urban regions.
Extracting the map of areas susceptible to floodwater spreading: The final map of areas susceptible to floodwater spreading were produced with two classes of appropriate and inappropriate floodwater spreading with the area of 436821 (34%) and 843941 (66%) hectares, respectively.
Results: The obtained results of this study indicated that considering the prioritization of effective factors in locating areas susceptible to floodwater spreading, the slope index, quaternary units, alluvium thickness and land capability had the weighted means of 52.5, 42.5, 38.5 and 27, respectively.
Regarding the slope map, the area of the mostly appropriate, somehow appropriate and inappropriate lands were approximately 489393, 15393 and 535271 hectares, respectively.
According to the quaternary units` map, the area of the mostly appropriate, somehow appropriate, appropriate and inappropriate lands were approximately 324680, 322418, 84825 and 548839 hectares, respectively.
Based on the alluvium thickness layer, the area of the mostly appropriate, somehow appropriate, appropriate and inappropriate (other areas lacking alluvium, which were located in the structure confining area) lands were approximately 324680, 322418, 84825 and 548839 hectares, respectively.
According to the land capability and resource map, the area of mostly appropriate, somehow appropriate, appropriate and inappropriate lands were approximately 122735, 70375, 123432 and 964220 hectares, respectively.
Therefore, the effective factors in locating areas for establishing floodwater spreading network as well as weighing and integrating prepared layers were investigated and the map of final zoned areas susceptible to floodwater spreading was provided, which showed that the administration of such plans in geographic information systems was possible and the obtained results enjoyed high accuracy.