Assessing of the Morphology and Sediment Transport of Diyala River

Wafeek Abood Jassam,Basim Sh Abed

doi:10.31026/j.eng.2021.11.04

Abstract

Diyala River is one of the important rivers that provide water for the Governorate of Diyala. In this research, the morphology and sediment transport of this river were studied using HEC-Ras software. The selected length of the river in the present study is 193 km and extended from Diyala Weir to the confluence of Tigris River and Diyala River. The fieldwork period extended from June 2020 till August 2020, where suspended-load and bed-load samples were collected and surveyed some cross-sections. The one-dimensional sediment transport model has been calibrated for five years, from 2014 to 2019. The results were compared with the measured cross-sections in 2019, and the suitable value of (maximum depth) was 120 cm for five years. The result of invert change from the simulation of the sediment model for real condition of the river from 2018 to 2019 ranged from0.2 m to 0.6 m. Moreover, the daily and yearly sediment discharge was equal to 227.7 tons/day and 83531.93 tons/year, which were previous studies carried out on this river. While the simulating results of the imposed period as five successive flood years give an invert change values varied from -1.25 to 1.4 m. The river's capacity was improved by rising the riverbank level for parts of the reach and/or training of cross-sections for other parts.

Highlights

The decreasing of flowrate in Diyala River, downstream of Diyala weir during the past dry years, after the flood of 1988, as well as the accumulation of sediment in the stream of the river for long periods due to the lack of maintenance in the river, led to a major change in the morphology of this river, which caused a reduction in the capability of the river to passes the flood waves
When simulating the actual condition of Diyala River for one year, the invert change values ranged from -0.2 m to 0.6 m, the maximum deposition depth value was equal to 60 cm, at station 141 km, located downstream of Diyala River
The used values of flowrates to simulate the actual condition in the Diyala River were measured by MoWR from Jun 2018 to May 2019 and ranged from 19 to 601 m3/s.The results showed that the daily sediment quantity varied from 14.73 to 1097.6 tons/day, and the average value of daily sediment discharge was equal to 227.7 tons/day

Summary

Introduction

The decreasing of flowrate in Diyala River, downstream of Diyala weir during the past dry years, after the flood of 1988, as well as the accumulation of sediment in the stream of the river for long periods due to the lack of maintenance in the river, led to a major change in the morphology of this river, which caused a reduction in the capability of the river to passes the flood waves. The selected length for the river in the present study was 193km and extended from Diyala Weir to the confluence end of Tigris River and Diyala River, Fig.. Some of the studies used other methods to estimate the value of sediment accumulation within the rivers. (Al-Ansari, et al, 1986) estimated the suspended sediment quantity lower of Diyala River. The selected river reach of the river extended from the Hemrin reservoir to downstream of Diyala Weir with a length equal to 50 km. (Azarang, et al, 2015) developed one-dimensional Version 4.1 of the HEC-RAS model to predict the reservoir dam's ability to protect the Karkheh River, located in Iran, by simulating erosion and sedimentation downstream of the river. According to the sediment results (Ackres-White, Larsen, and Engelund-Hansen) formulas had an accurate prediction of sediment transport and erosion in the Karkheh River since the Nash-

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Conclusion