Ecohydrological and morphological relationships of a regulated lowland river; based on field studies and hydrological modeling

• The ecohydrological status of the small and medium streams can describe together with static and dynamic characteristics.
• The depth-to-width ratio and the Slope-to-Froude number ratio are useful for estimating the natural hydrologic condition of regulated streams.
• The multivariate analyses of the one-dimensional modelled data rows describe the three-dimensional nature of streams.
• The vegetation and the riverbed roughness are among the primary ecohydrological characteristics.

The planning of the correct channel reconstruction is a priority in the rehabilitation of regulated surface streams. The present study examines the most important morphological and ecohydrological factors of a highly modified watercourse. A comparative analysis was performed among modelled and measured morphological, river geometrical, hydraulic, and vegetation status indicators. Reduction of data redundancy and examination of the relationships was done by factor analysis. This was found during the data reduction to six or seven attributes (component) and it was sufficient for imaging the original information content. There are mathematically derived hydrological background variables that are extremely significant in characterizing the watercourses, for example; the Reynolds number, Froude number, ratio of slope Froude-number, speed-to-depth ratio, depth-to-width ratio, etc. The partially regulated and artificial river sections were numerically separated from each other in the analysis. The functional aquatic plant habitats and Manning’s n Roughness have got a higher factor weight in the less regulated river section, than in artificial stage. The weakest factor weights were those status indicators which were most changed by the regulations. The results provide support for defining and monitoring the required environmental geometric riverbed interventions.