ABSTRACT

The knowledge of flood-induced ground effects and flood-water dynamics is a crucial issue for hydro-geomorphic hazards assessment and mapping, and thus for river management and land use planning. This paper and the related 1:15,000 map illustrate the lower Orba River (NW Italy) and its adjacent floodplain geomorphic response to the 21–22 October 2019 extreme flood. This was estimated to be a 500-years flood and caused severe damage to cultivated fields, structures, and infrastructures. The research is based on extensive post-flood field surveys, ante- and post-flood GNSS surveys, and aerial photographs interpretation. Intense in-channel sediment mobilization, bank retreats, and channelization structures collapses were surveyed. Furthermore, alluvial gullies, overbank deposits, crevasse splays, and surficial-erosion evidences were mapped over the floodplain, along with the flooded area (17.65 km²) and the flood-water features. A specific legend developed for flood-related and anthropogenic elements mapping in a typical lowland agricultural landscape with regulated rivers is proposed.

摘要

洪水诱发的地面效应和洪水动态的知识是评估水文地貌危害和制图的关键问题，因此对于河流管理和土地利用规划也至关重要。本文和相关的1：15,000地图说明了奥尔巴河下游（意大利西北部）及其对2019年10月21-22日的特大洪水的邻近洪泛区地貌反应。据估计，这是500年的洪灾，对耕地，建筑物和基础设施造成了严重破坏。该研究基于大量的洪水后实地调查，洪水前和洪水后GNSS调查以及航空照片解释。调查了强烈的河道内泥沙动员，河岸撤退和河道化结构塌陷。此外，冲积沟，过高的存款，裂隙八达通，²）和洪水特征。提出了一个特殊的图例，该图例用于在河流受管制的典型低地农业景观中绘制与洪水有关的和人为因素。