Climate change has led to alterations in precipitation patterns, with an increase in extreme rainfall events and the emergence of drought trends. These changes have significantly increased the risk of flooding in streams, particularly in residential areas. Consequently, the evaluation of stream rehabilitation must extend beyond the confines of hydraulic conveyance capacity, encompassing hydro-geomorphological stability, ecosystem services, and socio-economic considerations. The present chapter delineates the engineering design principles for structures employed in the context of stream restoration, with a particular emphasis on the integration of hydraulic, ecological, and morphological processes. The discussion focuses on the equilibrium between conventional hard-engineering interventions and process-based, nature-based approaches, with particular emphasis on cross-section design, flow-velocity control, and bed and bank stability. A case study from the Darveta and Köyiçi Streams in Halkalı Village (Elazığ, Türkiye) is examined, including Q₁₀₀-Q₅₀₀ design discharges, Manning roughness estimation using the Cowan method, hydraulic performance of culverts, grade-control weirs, concrete bed lining, and stability analyses of 1.60 m high retaining structures. The study emphasises the necessity of an engineering-driven yet interdisciplinary framework that collaboratively addresses flood safety and ecological functionality.