Midchannel islands in lowland river corridors and their impacts on flow structure and morphology:A numerical based conceptual analysis

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dc.contributor.authorHeidari, Naghmeh
dc.contributor.authorYagci, Oral
dc.contributor.authorAksel, Murat
dc.date.accessioned2026-01-24T12:31:08Z
dc.date.available2026-01-24T12:31:08Z
dc.date.issued2021
dc.departmentAlanya Alaaddin Keykubat Üniversitesi
dc.description.abstractMidchannel islands (MCIs) are influential geomorphic units in regulating morphological and ecological dynamics in sand-dominated rivers. The primary objectives of the study were to understand a) the relationship between morphometric characteristics of the basin and the occurrence location of the MCIs, b) the role of MCIs on the hydraulic gradient and the other hydraulic variables along the reach, and c) the influence of island growth process on hydrodynamics in the wake and contraction regions. Spatial distributions of MCIs depending on the morphometric features of the three characteristic basins were considered. While the basin-scale analysis was conducted using GIS-based data, the reach and individual scale analyses were performed based on a Reynoldsaveraged Navier-Stokes (RANS) model. Uniform circular cylinder and island geometries were exposed to identical flow conditions. The expansion of these island geometries was mimicked both in rectangular and trapezoidal cross-sections. The variation of water surface slope and bottom shear stress variables, which greatly trigger the intensive bilateral interaction between hydrological-morphological-ecological elements in river corridors, depending on the growth of the island, was determined. The role of imposed island geometry on the secondary flow structure within the downstream cross-section of the island and streamwise velocity fluctuations in contraction regions were analyzed. The basin-scale analysis showed that with decreasing basin slopes, the family of islands emerged at a longer distance to the basin outlet. It was also seen that MCIs location is closer to the basin outlet forbasins with a lower aspect ratio. Besides, asymmetrical large-scale counter-rotating streamwise vortices were detected behind the MCIs based on numerical simulations. GIS-based data showed that this coherent flow structure brought about channel adjustments in downstream of the island. In addition to morphological consequences, it was hypothesized that this alteration in the flow structure due to MCI has potential impacts on riverine ecology. These impacts are increase in groundwater recharge, vertical exchange of surface-subsurface water, local heterogeneity in sediment characteristics (i.e., convenient fish spawning areas), and enlargement in the hyporheic zone.
dc.identifier.doi10.1016/j.ecoleng.2021.106419
dc.identifier.issn0925-8574
dc.identifier.issn1872-6992
dc.identifier.scopus2-s2.0-85114828614
dc.identifier.scopusqualityQ1
dc.identifier.urihttps://doi.org/10.1016/j.ecoleng.2021.106419
dc.identifier.urihttps://hdl.handle.net/20.500.12868/5676
dc.identifier.volume173
dc.identifier.wosWOS:000704979200007
dc.identifier.wosqualityQ2
dc.indekslendigikaynakWeb of Science
dc.indekslendigikaynakScopus
dc.language.isoen
dc.publisherElsevier
dc.relation.ispartofEcological Engineering
dc.relation.publicationcategoryMakale - Uluslararası Hakemli Dergi - Kurum Öğretim Elemanı
dc.rightsinfo:eu-repo/semantics/closedAccess
dc.snmzKA_WoS_20260121
dc.subjectChannel incision
dc.subjectEcology
dc.subjectMidchannel bar
dc.subjectMorphology
dc.subjectRiver secondary flow
dc.subjectBottom stress
dc.titleMidchannel islands in lowland river corridors and their impacts on flow structure and morphology:A numerical based conceptual analysis
dc.typeArticle

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