پديد آورندگان :
جوكارسرهنگي، عيسي نويسنده دانشيار گروه جغرافيا، دانشگاه مازندران , , عليزاده ، عبداله نويسنده دانشجوي كارشناسي ارشد ژيومورفولوژي، دانشگاه مازندران ,
كليدواژه :
ارزش اطلاعات , ريزش , فرايند تحليل سلسلهمراتبي , هراز
چكيده فارسي :
يكي از انواع حركات دامنه اي كه در مناطق كوهستاني خسارت هاي جاني و مالي فراواني وارد مي كند، ريزش هاي سنگي است. شناخت نواحي حساس به ريزش با بهره گيري از روشهاي دقيق و مناسب براي تردد جاده اي و همچنين ساكنان منطقه، اهميت زيادي دارد. هدف از اين پژوهش بررسي عوامل موثر در وقوع ريزش و تهيه نقشه پهنه بندي خطر آن در دره هراز، واقع در استان مازندران است. براي اين كار، نخست با استفاده از تصاوير ماهواره اي و بررسيهاي ميداني، نقشه پراكنش ريزش هاي منطقه تهيه شد. سپس نقشه هاي عوامل موثر بهمنزله لايههاي اطلاعاتي در محيط GIS وارد شدند. پس از محاسبه فراواني ريزشهاي موجود در هر طبقه از عوامل و وزن دهي به آنها، با استفاده از مدل ارزش اطلاعات، لايه هاي ساختهشده در محيط ArcGIS با هم تلفيق و از جمع جبري نقشههاي وزني، نقشه پهنهبندي خطر ريزش در منطقه تهيه شد. براي تهيه نقشه پهنه بندي با استفاده از روش تحليل سلسلهمراتبي، وزن هر عامل از ماتريس وزن دهي بهدست آمد. نتايج بيانگر آن است كه بهترتيب عوامل شيب، جنس سنگ، پوشش و كاربري زمين، جاده، آبراهه، گسل، ارتفاع و جهت دامنه، بيشترين نقش را در وقوع ريزش در منطقه دارند. ارزيابي مدل ها نشان داد كه مدل هاي ارزش اطلاعات و تحليل سلسلهمراتبي، بهترتيب با احتمال تجربي 737/0 و 842/0 براي پهنه بندي در منطقه مناسب هستند؛ اما در مقايسه، وزن دهي عوامل با استفاده از تحليل سلسلهمراتبي موجب افزايش دقت كار شده است.
چكيده لاتين :
Introduction
Rockfall is one of the main slope movement processes in the natural evolution of rocky mountain slopes. Rockfalls are natural geomorphological processes that cause different types of damage and affect people, organizations, industries and the environment. There are various methods to susceptibility mapping including the following: semi qualitative methods similar to the analytical hierarchy process (AHP), bivariate statistical analysis, the probability–frequency ratio model and multivariate regression methods such as logistic regression. The purpose of this research is to produce of Rockfall susceptibility mapping by information value and AHP models in GIS environment in the Haraz valley.
Methodology
The study area lies between the latitudes of 35° 46? N to 36° 11? N and longitudes of 52° 01? E to 52° 23? E. Main stream in the area is Haraz River. Topographic elevations in the study area vary between 481 to 3410 m. This study describes the application of information value and AHP models to rock-fall susceptibility mapping along of Haraz valley and road in province mazandaran. in order to prepare the zonation mapping of Haraz valley, Rockfall distribution map were supplied. For this purpose, firstly, a detailed Rockfall inventory map of the study area is prepared by means of extensive field and air photography studies. Rockfall conditioning parameter maps are prepared from Digital Elevation Model (DEM) and from existing thematic maps of the study area , the map was verified by comparing with existing Rockfall locations for calculating prediction accuracy. Then the map of effective factors were used as information layers. The spatial relationship between the rockfall location and each Rockfall-related factor were analyzed by using the probability frequency ratio. The frequency ratio, a ratio between the occurrence and absence of Rockfall in each cell, was calculated for each factor’s type or range that had been identified as significant with respect to causing Rockfall. Frequency ratio for each factor’s type or range was calculated by dividing the landslide occurrence ratio by the area ratio. After calculating frequency of the Rockfalls in each class of factors and determining their weight using information value model, the developed layers in Arc GIS Were integrated, Rockfall hazard maps was provided.
Results and Discussion
To determine the factors influencing rockfalls, data layers of elevation, slope, aspect, lithology, distance to fault, distance to road, land use and were distance to river analyzed through overlaying the dispersion map of rockfall. The results showed that elevation of 800-1200 meters, slope higher 85 percents, the west direction, Limestone, marl, marly limestone Formation, distance of 500 meters from fault, distance of 300 meters from road and river and finally land use Moderate range are appropriate to rockfall. The results are shown as table and rockfall susceptibility maps.
Conclusion
In this study, Prioritization of Rockfall Effective Factors using AHP Model showed that slope, lithology, land use, distance to road, distance to river, distance to fault, elevation and aspect were found to be the most important factors affecting rockfall. The results are shown as five classes of rockfall susceptibility. Evaluation of these models indicated Information Value and AHP models with empirical probability of 0.737 and 0.812, respectively are appropriate for zonation. However, in comparison, the AHP Model has a higher efficacy in zonation.
