Sediment transport modelling at river confluence using HEC-RAS2D

• Autorzy: Tunas I. Gede , Herman Rudi , Arafa Yassir

Identyfikatory

DOI

10.12912/27197050/199510

• Języki publikacji: EN

Abstrakty

EN

Sediment deposition is a serious issue in river channels, especially at river confluences. Massive sediment deposition triggered by flow stagnation causes changes in riverbed cross-section and morphology. The capacity of the river cross-section decreases along with the increase in sediment deposition in the area. This paper aims to simulate sediment transport at the confluence of the Palu and Sombe-Lewara Rivers, one of the rivers with sedimentation issues in Central Sulawesi, Indonesia. The simulation is performed with the HEC-RAS2D model to predict sediment transport rates and bed morphology changes due to flooding. Supporting data for this model are discharge data transformed from rainfall data with a return period of 50 years, DEM data generated from field measurement data, and sediment grain gradation data obtained from sieve analysis of field sediment samples. The formation of mesh/grid as the basis for numerical modeling is performed on the RAS Mapper module based on DEM data of the study area. The DEM resolution is a reference in determining the mesh/grid distance which will ultimately affect the accuracy of predictions of water level, sediment transport and bed morphology changes. Calibration has also been done by assessing observed and simulated water levels and obtaining the optimal Manning roughness coefficient of 0.037. The results of the study indicate that the flow velocity is distributed in the transverse direction at the river confluence. The velocity increases on the left and right sides of the stagnation line, respectively reaching 3.5 m/s and 5.7 m/s at discharge in the Sombe Lewara River of 40 m³/sec and 650 m³/sec in the Palu River. Furthermore, the velocity gradually decreases towards the river bank along with the decreasing influence of secondary currents. The sediment transport rate at the river confluence is 0.21 m³/s and 1.45 m³/s respectively, comparable to the sediment supply from the upstream catchment. The sedimentation pattern follows the velocity distribution where the riverbed is graded on the left side of the flow stagnation line reaching 1.2 m.

Słowa kluczowe

EN

bed morphology; stream juction; secondary; 2D modelling

• Wydawca: Lubelski Oddział Polskiego Towarzystwo Inżynierii Ekologicznej ; Lublin University of Technology ; WNGB Wydawnictwo Naukowe
• Czasopismo: Ecological Engineering & Environmental Technology
• Rocznik: 2025
• Tom: Vol. 26, iss. 3
• Strony: 70--80
• Opis fizyczny: Bibliogr. 22 poz., rys., tab.

Twórcy

autor

Tunas I. Gede

• Department of Civil Engineering, Faculty of Engineering, Universitas Tadulako, Kampus Bumi Tadulako Tondo, Jalan Soekarno - Hatta Km.9 Palu, Central Sulawesi, 94117, Indonesia

• https://orcid.org/0000-0001-5168-4455

autor

Herman Rudi

• Department of Civil Engineering, Faculty of Engineering, Universitas Tadulako, Kampus Bumi Tadulako Tondo, Jalan Soekarno - Hatta Km.9 Palu, Central Sulawesi, 94117, Indonesia

• https://orcid.org/0009-0004-8833-532X

autor

Arafa Yassir

• Department of Civil Engineering, Faculty of Engineering, Universitas Tadulako, Kampus Bumi Tadulako Tondo, Jalan Soekarno - Hatta Km.9 Palu, Central Sulawesi, 94117, Indonesia

• https://orcid.org/0000-0003-3622-6434

Bibliografia

• 1. Ali, H.L., Yusuf, B., Mohammed, T.A., Shimizu, Y., Razak, M.S., and Rehan, B.M. (2019). Assessment of vanes effectiveness in controlling erosion and deposition zones at a river confluence using a 2D model. International Journal of Integrated Engineering, 11(2): 223–235. https://doi.org/10.30880/ijie.2019.11.01.024
• 2. Al-Jubouri, M., Ray, R.P., and Abbas, E.H. (2024). Prediction of scour depth for diverse pier shapes utilizing two-dimensional Hydraulic Engineering Center’s River Analysis System sediment model. Fluids, 9(11): 1–18. https://doi.org/10.3390/fluids9110247
• 3. AlQasimi, E., Mahdi, T.F. (2020). Rivers’ confluence morphological modeling using SRH-2D. Advances in Natural Hazards and Hydrological Risks: Meeting the Challenge, 171–176. https://doi.org/10.1007/978-3-030-34397-2_33
• 4. Baranya S., Olsen N.R.B., and Józsa J. (2015). Flow analysis of a river confluence with field measurements and RANS model with nested grid approach. River Research and Applications, 31(1): 28–41. https://doi.org/10.1002/rra.2718
• 5. Chabokpour, J., and Azamathulla, H.M. (2022). Numerical simulation of pollution transport and hydrodynamic characteristics through the river confluence using FLOW 3D. Water Supply, 22(10): 7821–7832. https://doi.org/10.2166/ ws.2022.237
• 6. Costabile, P., and Macchione, F. (2015). Enhancing river model set-up for 2-D dynamic flood modelling. Environmental Modelling & Software, 67, 89–107. https://doi.org/10.1016/j. envsoft.2015.01.009
• 7. Czuba, J.A., David, S.R., Edmonds, D.A., and Ward, A.S. (2019). Dynamics of surface-water connectivity in a low-gradient meandering river floodplain. Water Resources Re-search, 55(3): 1849–1870. https://doi.org/10.1029/2018WR023527
• 8. de Arruda Gomes, M.M., de Melo Verçosa, L.F. and Cirilo, J.A. (2021). Hydrologic models coupled with 2D hydrodynamic model for high resolution urban flood simulation. Natural Hazards, 108: 3121–3157. https://doi.org/10.1007/ s11069-021-04817-3
• 9. Hackney, C.R., Darby, S.E., Parsons, D.R., Leyland, J., Aalto, R., Nicholas, A.P., and Best, J.L. (2018). The influence of flow discharge variations on the morphodynamics of a diffluence confluence unit on a large river. Earth Surface Processes and Landforms, 43(2): 349–362. https://doi.org/10.1002/esp.4204
• 10. He, H., Tia, Y.Q., Mu, X., Zhou, J., Li, Z., Cheng, N., Zhang, Q., Keo, S., and Oeurng, C. (2015). Confluent flow impacts of flood extremes in the middle Yellow River. Quaternary International, 380–381: 382–390. https://doi.org/10.1016/j.quaint.2015.01.048
• 11. Ludeña, G.S., Cheng, Z., Constantinescu, G., and Franca, M.J. (2017). Hydrodynamics of mountain river confluences and its relationship to sediment transport. Journal of Geophysical Research: Earth Surface, 122(4): 901–924, https://doi.org/10.1002/2016JF004122
• 12. Martín-Vide, J.P., Plana-Casado, A., Sambola, A., and Capapé, S. (2015). Bedload transport in a river confluence. Geomorphology, 250: 15–28. https://doi.org/10.1016/j. geomorph.2015.07.050
• 13. Nicoară, Ş.V., Lazăr, G., and Constantin, A.T. (2018). Comparative study of a 1D and 2D numerical analysis modelling a water flow at a river confluence under accidental high waters. Hidraulica, 4: 90–97.
• 14. Penna, N., De Marchis, M., Canelas, O.B., Napoli, E., Cardoso, A.H., and Gaudio, R. (2018). Effect of the junction angle on turbulent flow at a hydraulic confluence. Water, 10(4): 1–15. https://doi.org/10.3390/w10040469
• 15. Schindfessel, L., Creëlle, S., and Mulder, T.D. (2017). How different cross-sectional shapes influence the separation zone of an open-channel confluence. Journal of Hydraulic Engineering, 143(9): 1–18. https://doi.org/10.1061/(ASCE) HY.1943-7900.0001336
• 16. Shen, X., Li, R., Cai, H., Feng, J., and Wan, H. (2022). Characteristics of secondary flow and separation zone with different junction angle and flow ratio at river confluences. Journal of Hydrology, 614(128537): 1–16. https://doi.org/10.1016/j.jhydrol.2022.128537
• 17. Sukhodolov, A.N., and Sukhodolova, T.A. (2019). Dynamics of flow at concordant gravel bed river confluences: Effects of junction angle and momentum flux ratio. Journal of Geophysical Research: Earth Surface, 124: 588–615. https://doi.org/10.1029/2018JF004648
• 18. Tunas, I. G., Ishak, M. G., Saparuddin, S., & Herman, R. (2024). Characteristics of bed profiles due to sediment transport in a debris river. Polish Journal of Environmental Studies, 33(2): 1347– 1356. http://dx.doi.org/10.15244/pjoes/170763
• 19. Tunas, I.G., and Maadji, R. (2018). The use of GIS and hydrodynamic model for per-formance evaluation of flood control structure. International Journal on Advanced Sci-ence, Engineering and Information Technology, 8(6): 2413–2420. https://doi.org/10.18517/ijaseit.8.6.7489
• 20. Tunas, I.G., Anwar, N. and Lasminto, U. (2019). A synthetic unit hydrograph model based on fractal characteristics of watersheds. International Journal of River Basin Man-agement, 17(4): 465–477. https://doi.org/10.1080/1571 5124.2018.1505732
• 21. USACE. (2023). HEC-RAS. HEC-RAS 2D sediment technical reference manual. Hydrologic Engineering Center, Davis USA.
• 22. Xie, Q.C., Yang, J., Lundström, T.S. (2020). Flow and sediment behaviours and morphodynamics of a diffluence−Confluence unit. River Research and Applications, 36(8): 1515–1528. https://doi.org/10.1002/rra.3697