Floods pose significant risks to cultural heritage (CH), yet post-disaster damage data on CH remain lacking. In this paper, we address this gap by focusing on the ex post assessment of flood-induced damage to CH. The method involves the identification of damaged assets and a field survey to assess loss in tangible value (LTV) and loss in intangible value (LIV). The potential contributing factors, e.g. water depth and river slope, are analysed through geospatial analysis. Ex post damage data on CH are compared with the outcome of an ex ante analysis based on available methods to verify the quality of exposure data and possible limitations. The method is applied to the 15–16 September 2022 flood event that occurred in the Marche region (Italy). The survey involved 14 CH in 4 municipalities and 3 catchments. Results highlight the inadequacy of existing exposure data for ex ante damage assessment and the importance of building characteristics. However, ex post data confirm that religious architectures are likely to suffer the highest LTV and LIV. The ex post damage analysis provided a semi-quantitative evaluation of both LTV and LIV in relation to flood characteristics. Notably, significant correlations between LTV and flood depth, as well as with the slope of the riverbed (a proxy for river flow velocity), were found. LIV correlates well to flood depth and river slope albeit with lower R² and larger RMSE, highlighting that intangible impact analysis requires more effort than hazard characterization. Further research should increase the availability of ex post damage data on CH to form the basis for damage model validation and development of empirical vulnerability functions.

On 27–28 July 2019, in a catchment of the Mt. Amiata area (Italy), an extreme rainfall induced a debris flow, which caused a channeled erosive process just upstream of the Abbadia San Salvatore village, the obstruction of a culvert at the entrance to the urban area, and the subsequent flooding of the village. In this paper, we present the back analysis of this event. The complexity of this case study is due to several peculiar characteristics, but above all, to the clogging of the culvert, a phenomenon difficult to simulate numerically. The methodology used for the reconstruction of the event is based on a multidisciplinary approach. A geological field investigation was carried out to characterize the catchment and assess the availability of debris. Then, a cascade of numerical models was employed to reconstruct the debris flow: the FLO-2D software was used to model the runoff along the hydrographic network while the mobile-bed debris flow TRENT2D model, available through the WEEZARD system, was used to quantify both the erosion and deposition processes that occurred during the event. To simulate the culvert clogging, a novel modelling procedure was developed and applied. Despite the challenging framework, the results, in terms of debris volume, erosion rates, deposition area, and timing of the culvert obstruction, agree reasonably well with the observed data. It is worth noticing that these results were obtained mainly using parameters set a priori, namely calibrated on a physical basis. This proves that the proposed methodology is robust and effective, with good predictive capability. Therefore, it may be considered, according to the European Union (EU) Flood Directive, an “appropriate practice and the best available technology that does not imply excessive costs” to support predictive hazard mapping of situations as the one here considered.

In urbanised areas, debris flows may encounter, along their path, closed sections due to culverted or buried streams. The solid phase can clog these sections, almost instantaneously transforming an effective work into a source of hazard. This condition requires particular attention in the design and model-based verification stage of these hydraulic works and needs advanced modelling approaches to describe the deposition process leading to clogging. In this work, we present a case study in the Abbadia San Salvatore town (Mt. Amiata, Italy), where a new culvert was realised after a debris flow event, which may potentially undergo clogging. Starting from the results of a previous study aimed at the back-analysis of a clogging event that occurred in 2019, this paper focuses on evaluating the susceptibility to clogging of the new culvert. Using the TRENT2D debris flow model, two scenarios were analysed: the former consisting of the sole new culvert and the latter considering an additional open check dam to be located upstream of the culvert. Results show that the first solution is effective, even though not providing a reasonable safety factor against clogging, while the second scenario provides a more robust configuration. Additionally, this study offers outcomes and considerations that can be used in a more general design context.

Floods pose significant risks to cultural heritage (CH), yet post-disaster damage data to CH remain lacking. In this paper, we address this gap by focusing on the ex-post assessment of flood-induced damage to CH. The method involves the identification of damaged assets, and a field survey to assess tangible (LTV) and intangible (LIV) damage. The potential contributing factors e.g., water depth and river slope, are analyzed through geospatial analysis. Ex-post damage data to CH are compared with the outcome of an ex-ante analysis based on available methods to verify the quality of exposure data and possible limitations. The method is applied to the 15–16 September 2022 flood event that occurred in the Marche Region (Italy). The survey involved 14 CH in 4 municipalities and 3 catchments. Results highlight the inadequacy of existing exposure data for ex-ante damage assessment. However, ex-post data confirm that religious architectures are likely to suffer the highest LTV and LIV. The ex-post damage analysis provided a semi-quantitative 15 evaluation of both LTV and LIV in relation to flood characteristics. Notably, significant correlations between LTV and flood depth, as well as with the slope of the riverbed (a proxy for river flow velocity), were found. LIV correlates well to flood depth and river slope although with lower R² and larger RMSE, highlighting that intangible impact analysis requires more effort than hazard characterization. Further research should increase the availability of ex-post damage data to CH to pose the basis for damage model validation and development of empirical vulnerability functions.

Mountain environments are naturally exposed to debris flows, a mass movement which represents one of the major geomorphological hazard sources for urbanized alluvial fan. In the last decades, climate change has contributed to extreme precipitations increase, making debris flows both larger and more frequent than in the past. The assessment and management of the risk associated with these events, according to UE Flood Directive, is feasible and desirable by using appropriate practices and the best available technology that do not imply excessive costs.In line with the above-mentioned European Directive, we present a multidisciplinary approach for the numerical modelling of the debris flow event that occurred on July 27-28, 2019 in Abbadia San Salvatore, a  village located in a catchment of the Mt. Amiata area (Southern Tuscany, Italy). Debris flow was triggered by an extreme rainfall of 110 mm/1 h causing a channelled erosive process, and the subsequent obstruction of a culvert at the entrance to the village, flooding and damaging it.Mt. Amiata is an extinct Pleistocene volcano mainly consisting of trachidacitic lavas characterized by a pervasive saprolite weathering, resulting in a large amount of residual loose debris resting on the hillslopes and along the hydrographic network. Specific geological and engineering-geological field investigations were carried out to assess the availability of debris material and its hydrological behaviour, providing more constraints for numerical modelling. The Green-Ampt model, implemented in the FLO-2D software, was used for the evaluation of discharge values in the hydrographic network. Subsequently, the debris flow modelling was conducted applying the WEEZARD system, composed of a previously developed advanced two-phase debris-flow model (TRENT2D), re-coded as a web service. The mass movement was simulated to quantify erosive and depositional processes that occurred during the event. In addition, a specific approach was implemented to model the effect of the culvert that was clogged during the event.Despite the challenging modelling aspects, the results in terms of debris volume, erosion rates, flooded area and timing of the culvert obstruction, are in agreement with observed data. The WEEZARD system has therefore proved to be an effective tool, in line with the indications of the European Directive. Moreover, the reconstruction was obtained using most of the a priori parameters setting. This shows that the used modelling approach has a good predictive capacity and can therefore be reasonably used to support further predictive hazard mapping analyses. Finally, another important element to be highlighted is that an accurate input model based on the integration of detailed geological-geomorphological investigations is necessary to obtain reliable modelling results.

The Alpi Apuane (Italy) are located a few kilometres from the coast of the Ligurian Sea, and they are characterized by peak elevations up to two thousand meters above sea level, as well as narrow, deeply incised valleys and steep slopes. Due to these morphoclimatic conditions, heavy rains are frequent, causing floods, landslides, and debris flows, particularly within the Vezza catchment. In this work we applied two different hydrological-hydraulic models to this catchment, focusing on the catastrophic debris flow event of June 19, 1996. Firstly, recent, well-documented rainfall events were used to validate the engineering geological model of the study area, then we began to analyse the rainfall-runoff and debris flow event of 1996 in the Cardoso sub-catchment. As models, we used the FLO-2D and a novel experimental model, developed by some of the authors and based on TRENT2D, in which the dynamic of a debris flow is fully coupled with the rainfall-runoff response of a basin. Preliminary results show how the used approach allowed us to gain some insight into the hydrological behaviour and debris flows formation, erosion, transport, and deposition in the Cardoso sub-catchment.