Effects of Physical development and urban land use change on Riparian Zone River; Case Study: Khoshk River in Shiraz City, Iran

The Khoshk river emanates from golestan and ghalat height and flow to the northwest and southeast direction. After traversing a short distance it cover's golestan and dukohak,goiom from the right and the ghasr ghomshe branch from the left. Then by direct cross from the middle of shiraz metro police, it will divide it into to half south and east and at the end, it will pour into maharlo lake.numorus researchs with different method and purposes has been done I. Side and outside of the country about the change of morphology and effective factors for them. The aim of this paper is investigating the changes of manipulation the zones in time-place range in the sanctum of the river.
The main researching method, in this paper is the traverseal and analytical method. Thus for determining the ranges in the limitation of the case we study about existing maps, scope revision and Google earth software have been used. And then the oldest satellite images of the zone (Lansat8 OLI imagery) have been provided for 1394 with the power of 30 meter state dividing coherent to Shiraz metropolis. By the use of geological maps and topography, air shots and satellite images of shiraz were studied and geomorphologic annotation of them were done about expanding the city in sanctum of the river as to recognize the changes of dry riverbed due to urban expanding in two time sections 1394 and 1346.
In this paper the riverbed divides in to 3 ranges as follow.
First range: the direction of chanarsookhte is from tange sorkh to Maliabad Bridge with 8 km long and average slope of 1.42%. Riverbed is formed by generally marine stages and Razak marine lime. The feature of this part of river is rash slope, severe erosion of near lands, brinding of strand. And the width of illuviation has been reported about 70 meters. The average of river's width on the air image in 1346 compared to 1394, has been reduced 19 meters. The space which the river has been changed to 56ha in 1394 which means 27.5 percent of river space has been reduced because of human operations in the sanctum of river, removing sand from the riverbed and the buildings.
Second range: from maliabad bridge to Fazilat Bridge is 15 km and the slope is 0.90%. In this direction, nahre azam sideway, ghoran gate, sadi, bajgah and etc pour in to Koshk River. Because of appropriate soil and enough mineral water, the gardens and agricultural lands has been expanded near the river. The property of this range is that the river's channel has been shored by the stile barrier. The narrow pass way of river channel, unsuitable bridges, floor fraction, lateral erosion of river, building sideways in both left and right shores of the river with the length of 7 km and urban buildings in the foot print of river. Thus most of the violation to the sanctum of river has been occurred in this range which has caused bad issues for Shiraz metropolis in the future.
The average width of river in 1394 compared to 1394 has been reduced 140 meters. And on the other side the space has been changed from 312 ha in 1346 to 92 ha in 1394 which means 70.5% of river's space has been reduced because of the change of controlling the lands due to human operation in the sanctum of river.
Third range:From the fazilat bridge to the exit of river from the city is 10 km in the length and 0.39 percent in average slope. The kind of bed's sediment is formed of torrential illuviation and kovaterner sediments. And the thickness of the illuviation has been reported 200 meter. The property of this part of low slope, is settling the sediments and reduction of river tension, low capacity at the time of big floodwaters.
Most of the river direction has been shored by the stile barrier and the mean width of river compared to second range is lower (42m) and it's mean depth compared to around deserts is 1.5m-2m. Nowadays the average river width compared to 1346 has been reduced about 49 meters. And the river's space in this range in 1346 is about 95ha but nowadays has been reached lower than 50ha. It means that 57% of river space has been decreased. Which by the effect of urban expanding and agricultural operations in this range has caused the constriction of the river pass way. As in every raining, it causes the uprising of river down the Sardkhane Bridge.
Investigating the changes of urban expanding effects and changing the lane controlling in the sanctum of Khoshk River, are the most important aims of this paper which has been evaluated. According to the results of urban expanding investigation in the first rang, there is Alluvial fan in the Foot of mountains foothill stone which is firmed by sediments, maren, shil and weak seeds articles. But in the second and third local sections, the city is placed in a desert zone which the kind if the sediments of illuviation articles are kovaterner. Urban expanding in the sanctum of river in the above time-local ranges causes the reduction of riverbed space compared to last year. In that the space of river bed has been reached from 77ha to 56 ha (27.5%) in the first range and from 312 to 92 ha (70.5%) in the second range and from 95 ha go 41 ha (57%) in third range. And also width displacement of the river was 176 meter in first range, 145 meter in the second range and 68 meter in the third range. In the past, the firm of city was nuclear and compressed and occupied lower space of river sanctum. The result is that the type of physical expanding of this city has been proceed thorough linear type.