Author(s): Helene Mueller; Anna Ludwiczek; Magdalena Von Der Thannen; Hans Peter Rauch

Linked Author(s):

Keywords: Urban stream; Water temperature; Soil and water bioengineering; Riparian vegetation; Ecological low flow; Slow hydrology

Abstract: Urban stream s are highly modified and hydraulically constrained yet increasingly affected by thermal stress during low-flow conditions. Restoration measures often slow flow and raise thermal sensitivity, while shading from riparian vegetation can mitigate heat inputs - but this vegetation frequently conflicts with hydraulic capacity requirements. This study quantifies the cooling effect of riparian vegetation during a the median river heat period (RHP) in 2015-2024 in the semi-urban Liesingbach (Vienna, Austria). Vegetation shading was derived from hemispherical photography, and water temperature was simulated for an 8.3 km reach using the HEC-RAS water quality module. Model calibration and validation against two RHPs showed good agreement. Removing riparian vegetation increased daily peak water temperatures by 1.3°C, demonstrating that even sparse tree lines or shrubby vegetation implemented trough soil and water bioengineering techniques provide meaningful thermal buffering. The results underscore the importance of integrating thermal considerations into urban river restoration, as shading can substantially reduce heat stress during critical low-flow periods while supporting ecological resilience.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.255

Year: 2026