Can the basin morphology alone provide an insight into floodplain delineation?

The present research was aimed to evaluate flooding exposure by exploiting the potential of morphological indices (e.g., drainage area, local slope, curvature, etc.). It was found that the areas exposed to flood inundation may be delineated quite well by adopting a modified topographic index computed from DEMs (Digital Elevation Models). Since the modified topographic index is sensitive to the spatial resolution of the digital elevation model, the scale dependence is investigated showing an increase in the performances of the method with the resolution of the DEMs. The procedure proposed is tested over the Arno river basin using the existing documentation on flooding exposure produced by the local River Basin Authorities. The use of the proposed modified topographic index may represent a useful and rapid tool in delineating the flood prone areas in ungauged basins and in areas where expensive and time consuming hydrological-hydraulic simulations are not possible.

How to cite: Manfreda, S., A. Sole, M. Fiorentino, Can the basin morphology alone provide an insight on floodplain delineation?, on Flood Recovery Innovation and Response (edited by C.A. Brebbia), WITpress, 47-58, 2008. [Link]


The objetive of the present research was the evaluation of the flood exposure of the Italian territory. For this reason, the national territory has been subdivided in national, interregional and regional catchments according to the actual legislation regarding the soil defence (Law 183 of 1989). Such approach has been used in order to organize, within a Geographical Information System, the existing cartographic and technical documentation on flood exposure and risk produced by the local Agencies recently instituted. Using this documentation, we obtained a partical coverage of the Italian territory that has been extremely useful to explore new methods to define areas where the flood exposure is relatively high. A new method is presented for the definition of the areas exposed to floods that is based on the geomorphological characteristics of the territory. In particular, it was found that the flooding areas can be delineated fairly well trough a modified topographic index ITm = ln(an / tan(b)), where a is the drainage area per unit contour length, tan (b) is the local slope in the steepest descent direction and n is an exponent that was found to be close to 0.15-0.20. Such analyses have been carried out using a digital elevation model at 230 m and one at 90 m of resolution produced by NASA.

How to cite: Manfreda, S., A. Sole, e M. Fiorentino, Valutazione del pericolo di allagamento sul territorio nazionale mediante un approccio di tipo geomorfologicoL’Acqua, N.4, 43-54, 2007. [pdf]