Assessment of Changes in the Diyala River Channel from Diyala Dam to Al-Sabtiyah Bridge and Their Environmental Implications

Abstract

This study evaluates the morphological changes in the Diyala River channel from Diyala Dam to Al-Sabtiyah Bridge and examines their environmental implications using Remote Sensing (RS) techniques and Geographic Information Systems (GIS) as the primary platform for spatial processing and analysis. The study relied on the digital analysis of satellite imagery covering the period from 2000 to 2025, in addition to topographic analysis and the construction of a Digital Elevation Model (DEM) for the area. The DEM revealed elevation variations ranging from 143 m above sea level at the highest point, near Diyala Dam to 33 m above sea level at the lowest point, near Al-Sabtiyah Bridge. This overall gradient constitutes the principal driver of the river's hydraulic energy, the area was classified into four slope categories: flat terrain (0–1°), representing the largest area and encompassing the floodplain surrounding the river; gently sloping terrain (1–3°); moderately sloping terrain (3–6°); and steep terrain (6–23°). The river channel was observed to be straight in areas with steep gradients, contrasting with a marked increase in meandering and sinuosity in flat or gently sloping areas To monitor changes, several selected cross-sections for the periods (2000) and (2025) were compared, the area was divided into three main stations, each comprising five cross-sections. The first station exhibited substantial channel widening across all five sectors. The fifth sector recorded the greatest increase, with the river width expanding from 74 m in 2000 to 1,006 m in 2025, representing an exceptional increase of 932 m. The first sector followed with an increase of 696 m (from 92 m to 788 m), while changes in the second, third, and fourth sectors ranged between 242 m and 346 m. This remarkable morphological expansion is primarily attributed to the interaction between natural processes and intensive human activities, particularly the uncontrolled proliferation of gravel and sand quarries, which have significantly altered the riverbanks and environmentally contributed to channel widening. The second station displayed a marked tendency toward channel meandering. The first sector recorded the greatest increase (33 m), closely associated with quarrying activities, followed by increases of 10 m and 12 m in the second and fourth sectors, respectively. In contrast, the third sector experienced a reduction of 24 m due to Sedimentation activity, while the fifth sector recorded a slight decrease of 1 m. The third station exhibited an entirely different trend, characterized by the absence of channel expansion across all five sectors owing to the dominance of depositional processes. Channel width decreased by 4 m, 19 m, and 18 m in the first, second, and third sectors, respectively, whereas the fourth and fifth sectors remained hydrologically stable, with no measurable change (0%). The study concludes that unregulated human interventions, particularly the widespread extraction of gravel and sand in the upper reaches of the river (the first station), have exceeded the influence of natural geomorphological processes in reshaping the river channel and substantially increasing its width, thereby posing significant environmental concerns. In contrast, the downstream stations exhibit a gradual recovery toward natural equilibrium through sediment deposition and enhanced hydraulic stability.