Reply to Marchi's comment on &quot;Geomorphic hazards and intense rainfall: the case study of the Recco Stream catchment (Eastern Liguria, Italy)&quot; by Faccini et al. (2012)

F Faccini,A Sacchini,A Robbiano

doi:10.5194/nhess-12-3171-2012

Abstract

“Geomorphic hazard and intense rainfall: the case study of the Recco Stream Catchment (Eastern Liguria, Italy)” (Nat. Hazards Earth Syst. Sci., 12, 893–903, 2012) presented the impact of a heavy and short rainfall event in the Ligurian area (NW Mediterranean). It triggered several shallow landslides and flooded a part of the Recco alluvial plain. In the last decades, such events are increasing in Liguria and in the Mediterranean. In the Recco Stream catchment, we analyzed the conditions of geomorphic hazard related to the recent intensification of heavy rainfalls. We demonstrated the inadequacy of the Basin Master Plan for the slope environment. In fact, most of the instability phenomena were triggered in areas classified with medium and low geomorphic hazard. In the section “Information about the target event rainfall” the triggering weather condition was considered. The pre-frontal thunderstorm super cell caused heavy and short rainfalls concentrated on a very narrow area. These phenomena occur particularly in the central area of Liguria, due to AlpineApenninic orography and the Ligurian Sea. The radar image in Fig. 3c of the paper shows this situation from a geographical point of view. The isoyeth map of the 1 June 2007 event (Fig. 3b) was drawn on the basis of rain gauges data recorded in the six surrounding weather stations (Chiavari, Genova, Bargagli, Colonia Arnaldi, Polanesi, Bavari). This is supported by a hyetogram recorded at Polanesi station, located in the lower part of the Recco Stream catchment. The flood peak discharge has been preliminarly assessed on a rainfall/runoff evaluation. Further analysis in an un-gauged stream can be carried out by means of post-flood topographic surveys; the peak discharge was assessed by using six significant hydraulic cross sections of the Basin Master Plan (Provincia di Fig. 1. Locations of cross sections in the Recco Stream channel network.

Highlights

Genova, 2002), drawing the flood marks surveyed (Fig. 1)
In the paper we highlighted some significant topics characterizing the geomorphic hazard of a part of the Mediterranean coastal area
As already discussed in other similar situations (Faccini et al, 2005, 2009), with regard to slope hazard geomorphic assessment, improvements of the Basin Master Plan are needed. Events such those recorded 1 June 2007 are more and more recurrent in Liguria and always show a similar triggering meteorological mechanism and ground effects concentrated in narrow areas (Fig. 3); the well-known flash floods of 2010 and 2011 events in the Genoa municipality and surrounding areas caused human losses (Sacchini et al, 2011; Faccini et al, 2012)

Summary

Introduction

2002), drawing the flood marks surveyed (Fig. 1). In this case the Recco Stream Catchment Master Plan has correctly assessed the geomorphic hazard related to flood (Fig. 2).

Results

Conclusion