Hydraulic Roughness Estimation Induced by Riparian Vegetation in Tuscany Rivers for Management Purposes

Riparian vegetation and its management on vegetated bank and floodplains can affect hydraulic and hydrologic characteristics of the river flow and can reduce or increase hydraulic risk, especially in downstream urban areas in small catchments. In the present work, roughness estimation has been carried out by applying models that take into account relatively simple descriptive parameters, i.e. the diameter d (m) and the spatial density of plants m (Np/m2). Vegetation density was gauged on homogeneous areas by using forest-related field surveys on river bank and floodplain on Tuscan rivers and creeks: Albegna river, Arbia stream, Ombrone Grossetano river, Ombrone Pistoiese stream and Tevere river. An alternative field survey method based on the MOTI app, developed by the School of Agricultural, Forest and Food Sciences HAFL of Zollikofen for forest environments, was tested to evaluate its performance in the riparian zone. This speditive approach can provide basal area, number of plants per hectare by using relascopic and optical theory to obtain the needed parameters for the most widespread roughness estimation models. Significant results were obtained for the m = f(d) relations, which lead to estimates of roughness and associated hydraulic risk, useful for management purposes.