Optimizing Hydraulic Performance and Sustainability of the Simike-Nzovwe Roadside Drainage System in Mbeya City, Tanzania Using HEC-RAS Modeling

Optimizing Hydraulic Performance and Sustainability of the Simike-Nzovwe Roadside Drainage System in Mbeya City, Tanzania Using HEC-RAS Modeling | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Optimizing Hydraulic Performance and Sustainability of the Simike-Nzovwe Roadside Drainage System in Mbeya City, Tanzania Using HEC-RAS Modeling Abdul Mohamed, Zacharia Katambara This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5599152/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The side drainage system along the TANZAM Highway section from Simike to Nzovwe River, extending approximately 1.85 km and featuring five circular culverts, was evaluated to assess its hydraulic performance and behaviour during rainfall events. Using the HEC-RAS model, the study analysed flow regimes, specific energy transitions, and sediment transport to identify design inefficiencies and propose optimization strategies. The model effectively captured key processes, revealing significant silt accumulation upstream of culverts due to subcritical flow (Fr 1). Hydraulic jumps observed near culverts caused turbulence, localized erosion, and debris deposition, with flow velocities decreasing from approximately 7 m/s to less than 1 m/s during transitions. Sensitivity analysis demonstrated that Manning’s roughness coefficient, channel slope, and culvert dimensions significantly influence flow behaviour, sediment accumulation, and erosion patterns. Based on these findings, the study recommends optimizing channel geometry by reducing side slopes, steepening longitudinal slopes, and enlarging culvert dimensions to enhance flow efficiency and minimize sediment deposition. Material selection, such as riprap for high-velocity zones and vegetative linings for low-velocity sections, is proposed to improve erosion resistance and promote ecological stability. Additionally, sediment traps and sustainable drainage practices are suggested to mitigate sedimentation and reduce maintenance demands. This study highlights the value of one-dimensional flow models like HEC-RAS in designing and maintaining efficient roadside drainage systems, providing actionable recommendations to improve hydraulic performance, reduce maintenance costs, and ensure environmental sustainability in similar contexts.. HEC-RAS modelling side drainage design supercritical to subcritical flow sediment accumulation hydraulic performance evaluation Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5599152","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":437029373,"identity":"7e578f4e-724e-4045-819e-bd92f4ed67cc","order_by":0,"name":"Abdul Mohamed","email":"","orcid":"","institution":"Mbeya University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Abdul","middleName":"","lastName":"Mohamed","suffix":""},{"id":437029374,"identity":"ed93ca8c-4573-4d98-97e3-1d5c4f0efd81","order_by":1,"name":"Zacharia Katambara","email":"data:image/png;base64,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","orcid":"","institution":"Mbeya University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Zacharia","middleName":"","lastName":"Katambara","suffix":""}],"badges":[],"createdAt":"2024-12-07 13:23:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5599152/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5599152/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":80609561,"identity":"7f13c776-e82e-4280-97db-d19e649c424b","added_by":"auto","created_at":"2025-04-15 07:31:57","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":771240,"visible":true,"origin":"","legend":"","description":"","filename":"OptimisingHydraulicPerformanceandSustainabilityoftheSimike2025327.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5599152/v1_covered_630a6bc4-0f85-4cb8-8659-3afc948bd176.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Optimizing Hydraulic Performance and Sustainability of the Simike-Nzovwe Roadside Drainage System in Mbeya City, Tanzania Using HEC-RAS Modeling","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"HEC-RAS modelling, side drainage design, supercritical to subcritical flow, sediment accumulation, hydraulic performance evaluation","lastPublishedDoi":"10.21203/rs.3.rs-5599152/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5599152/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe side drainage system along the TANZAM Highway section from Simike to Nzovwe River, extending approximately 1.85 km and featuring five circular culverts, was evaluated to assess its hydraulic performance and behaviour during rainfall events. Using the HEC-RAS model, the study analysed flow regimes, specific energy transitions, and sediment transport to identify design inefficiencies and propose optimization strategies. The model effectively captured key processes, revealing significant silt accumulation upstream of culverts due to subcritical flow (Fr\u0026thinsp;\u0026lt;\u0026thinsp;1) and erosion risks in steeper sections with supercritical flow (Fr\u0026thinsp;\u0026gt;\u0026thinsp;1). Hydraulic jumps observed near culverts caused turbulence, localized erosion, and debris deposition, with flow velocities decreasing from approximately 7 m/s to less than 1 m/s during transitions. Sensitivity analysis demonstrated that Manning\u0026rsquo;s roughness coefficient, channel slope, and culvert dimensions significantly influence flow behaviour, sediment accumulation, and erosion patterns. Based on these findings, the study recommends optimizing channel geometry by reducing side slopes, steepening longitudinal slopes, and enlarging culvert dimensions to enhance flow efficiency and minimize sediment deposition. Material selection, such as riprap for high-velocity zones and vegetative linings for low-velocity sections, is proposed to improve erosion resistance and promote ecological stability. Additionally, sediment traps and sustainable drainage practices are suggested to mitigate sedimentation and reduce maintenance demands. 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