ارزیابی مخاطره زمین‌لغزش در ارتباط با توسعه شهری پاوه

Introduction

Anthropogenic impacts on the natural environment can lead to interference and increase vulnerability in the landscape and affect ecosystem services, environmental health and environmental sustainability. Increasing knowledge of the interconnected nature of many human and environmental issues has encouraged natural scientists (such as hydrologists, geomorphologists, and physical geographers more broadly) to work with social scientists (such as economists and human geographers) and engineers (such as designers). Environment, city planners) and policymakers to create an integrated interdisciplinary framework to meet new research needs. Urban geomorphology is an interdisciplinary field which is rapidly evolving and examines the effects (positive and negative; direct and indirect) of urbanization on the natural forms of the earth (geomorphology) and man-made structures (urban morphology), the processes that control their development in a given region. The city of Paveh is a vital human center in western Iran, located in the mountainous region of Shahu in the northwest of Kermanshah province, 20 km from the international border of Iraq at an altitude of 1600 meters. This study aims to evaluate the capacities and bottlenecks of sustainable urban development in Paveh city with the approach of geomorphological hazards. The ultimate goal of this study is to improve geomorphological awareness in order to understand the interaction between landforms, urban evolution and effective geomorphological processes, as a first step towards risk management and strategic protection of Paveh urban center.
Material and methods
The present study is an applied research. In this study to evaluate and zoning landslide risk 12 variables affecting the occurrence of this geomorphological phenomenon including altitude, slope, aspect, lithology, land use, stream power index, topographic wetness index, topographic position index, distance from fault lines, distance from hazardous road points, normalized vegetation index and land curvature were examined. The required data were obtained from 1: 100000 scale geological maps, images of digital elevation model of the region with a resolution of 12.5 meters related to ALOS-PALSAR satellite, hydrological data and field studies as well as library resources. Geomorphological map of the region was drawn using field studies and satellite images. To prepare thematic layers and implement research models, Arc GIS, ENVI and Surfer software were used. VIKOR method was used to zoning and spatial prediction of landslide occurrence.
Results and discussion
Currently, the city of Paveh is facing problems and issues such as increasing population, reducing geomorphic potencial, increasing the load on the slopes, all of which confirm that the natural bed of the city of Paveh is more unstable. Most residential areas in the region are located on the slope unit. Changes in geomorphic units have caused changes in other loops of natural systems and ultimately altered the dynamics and morphogenesis of the city. Based on field studies and geomorphological map of the study area, the most important hazards threatening the sustainable urban development of Paveh can be listed as follows:
Topographic restrictions and urban development of Paveh, Changing the natural cover of the earth and changing geomorphological trends, urban decay problems against environmental hazards, Urban construction weight and geomorphological changes, Non-standard slopes and creating limits to sustainable urban development, Sliding vulnerabilities of settlements and landslide hazard. The geomorphological map of the study area shows the presence of talus slopes in the northern parts of the region, which are the result of high temperature fluctuations in the Biston limestone formation. Several landslides have occurred in the southern parts of the region (Ilam Formation) and the northern slopes of Dourisan as a result of high slopes and possibly heavy rainfall events. Ridge valleys are one of the most important limitations of development in the northern parts of Paveh, Nouriab and Dourisan basins. A clear example of the ridge valleys can be seen in the neighborhood of the Grand Mosque, which has caused the destruction of urban uses, especially the asphalt and paving surfaces of the alleys. By examining the slip risk classes in the study area and comparing them, it can be seen that the areas where there are high and very high risk classes are on slopes above 40%;. The sensitivity of geological formations to degradation and weathering has caused the accumulation of large volumes of material on the slopes with other conditions (creating roads and fragmentation of slopes and heavy rainfall) may cause many landslides. In the northwestern part of Dourisan basin, due to severe temperature fluctuations, favorable conditions have been provided for landslides and rockfall. Landslides with a high probability of landslides are seen as relatively large spots. Excavation and trenching on Shahu Road, the presence of locally aerated and detached formations and slopes of 35 to 65 degrees can lead to local instabilities in this area. Due to the high probability of occurrence of Mass wasting hazard in Paveh, the amount of suitable land for the future development of the city is very small.
Conclusion
Due to the increasing physical development of Paveh city and the general tendency to settle in foothills in the future, human activities will play an effective role in the occurrence of geomorphological hazards. Based on the findings of the research, urban development in Paveh is moving with the destruction of garden and agricultural lands and moving towards unstable lands (slope of more than 35%). Landslide hazard map showed that the high-risk zone covers more than 40 square kilometers (43%) of the study area. Therefore, the current bed of the city of Paveh is at risk due to extensive processes, so that 39% of the area of the city is located in high-risk landslides. With the development of Paveh towards areas with high slope gradients, especially in the northern and eastern parts, the new settlements will be completely in the high-risk area of landslides.