地理と自然災害のジャーナル
オープンアクセス

概要

Temporal and Spatial Variations of Zarrineh-Rood River Morphology Using RS and GIS

Ebrahim Brooshkeh and Reza Sokuti

Identification of changes and their effects on the morphology of river bed and riverside lands is a necessity for river management. This study focuses to identify the trend of river morphological evolution and changes in the riverbed territory at the final 25-kilometer downstream section of the Zarrineh-rood River leading to Urmia Lake in West Azerbaijan during the last 50 years using aerial photos taken in 1955 and 1967, topography maps produced in 1996, and SPOT satellite images taken in 2011 with field survey. They were interpretated to 3 land types of sandy beaches, permanent riverbed and sandy barriers. Distinguished land type maps overlayd and compared using GIS ILWIS software. Surface area of land types, river meandering and sinusoidal coefficients were calculated and the trend of the river interpretated. Results showed that the area of the riverbed territory has reduced form 561.1 to 221.3 ha, and the riverbed morphology and the shape of river bends have evolved. From 1967 to 2011, natural features such as sand dunes inside the riverbed have reduced from 13.68 to 2.86 ha, which indicates high fluctuations of discharge and changes in hydrological and hydraulic conditions of the river. The number of meanders has decreased from 4 to 3 and the riverbed has become straighter and more arterial. Land types surface area of sandy beaches decreased from 503.66 to 140.78, permanent riverbed increased from 54.83 to 77.68 and Sand dune is almost stable. The sine coefficient of the river is about 1.5 that indicates river classified as meandering. Deposition plays a mail role in morphological changes. 60% reduction in the riverbed territory is alarming, and current riverbed with its sedimentation prone conditions will not be able to discharge floods with average and above average return period. The most effective factors in morphological changes are the changes in hydrological regime because of dam construction, reduction of runoff, and accumulation of sediment loads on the riverbed.