The Physical Development of Mashhad Metropolis and Change in the Morphology of River Systems

In terms of geographical location, Mashhad metropolis has spread all over a wide alluvial plain. Locating between the Kopeh Dagh and the Hezar Masjed sedimentary heights and the Binalood igneous heights has led to the creation of specific morphology for the Mashhad alluvial plain. In the northern part of the city, the Kashafrood River drains all the rivers of Mashhad plain. And the Binalood heights drainage rivers run through the city of Mashhad and drain into the Kashafrood River. The city's physical development over the years has led to a change in the morphology of the city's rivers and in some ways, high-rise buildings are built on the abandoned river-beds and the probability of occurrence of geomorphological hazards has increased. In this research, the location of Mashhad and its physical growth, which led to the destruction and change of river's morphology, has been studied by using 1353, 1359, and 1390 satellite images and the old maps of Mashhad and geological and topographic maps in different periods. The purpose of this research is to investigate the comparative situation of rivers with urban built canals and the resulting risks. In this regard, it has been found that many urban canals are designed without regard to the natural morphology of the rivers and also regardless of the flow capacity of the water. The natural type of the river-beds has been sedimentary deposits including shale, clay and sand and rock along with the forms between the rifting of the rivers, but the canals have thick concrete walls and direct paths.