تأثيرات الطبوغرافية, استخدام الاراض والتغير المناخي على تصريف مياه الامطار تحت شدات مطرية مختلفة في منطقة الأمير في مدينة النجف

Rp-Effects of Topography, Land use and Climate change on storm water drainage under Different Rainfall Intensities in AL-Ameer District in city.pdf

Stormwater drainage system flooding is a major problem in urban development that can be affected by land use, climate change, and topography. Flood problems can be successfully assessed using simulation models such as the Stormwater Management Model (SWMM). In this study, the generation of intensity-duration-frequency (IDF) curves integrating the impact of climate change for the Najaf Governorate in Iraq was performed for the first time. In addition, the impacts of different conditions of land-use (50, 75, and 100%), climate change (2, 5, 10, and 25 years), topography slope (0.5% to 0.4%, 0.3%, 0.2%, and 0.1%), and concentration time (downstream and upstream) on the stormwater drainage system were evaluated using SWMM simulation. Results indicated that by increasing the sub-catchment area from 50 to 100%, there was an increase in total runoff from 20,380 to 37350 m3, and total flooding from 10,513 to 26032 m3, respectively. In response to climate change, changing the return period from 2 to 5 years increased total runoff from 14,120 to 27,110 m3 (representing 48% of the increase), and total flooding increased from 5,914 to 17,591 m3 (representing 66.66% increment). Generally, sub-catchment slope positively affected flooding at all rainfall intensities, but had less effect at low rainfall intensities. In a two years return period, the effect of sub-catchment slope was limited with high flood reduction, whereas low sub-catchment slope had a little effect on flooding at return period of 10 and 25 years. Finally, the rise of the sub-catchment slope is observed leading to a further increase in runoff, which leads to flooding. The results also showed that the flood time occurs downstream before the upstream, indicating that the downstream region suffers from topographic and design problems. This was illustrated by manhole R315 flooding before manhole R15 because the slope of the sub-catchment is in the opposite direction of flow in pipes, as well as the depth of the manhole, is short.To conclude, as flooding locations and magnitudes were identified, the system fails to discharge stormwater under some critical conditions, and the adverse effect of the climate change on the stormwater drainage system was more than the effects of land-use. Also, the designers must match the sub-catchment with network pipe slops to reduce floods.