The Case Study site of Porto Garibaldi-Bellocchio is a 9km stretch of coast, located in the Ferrara and Ravenna provinces, in the region of Emilia-Romagna, northern Italy, facing the Northern Adriatic Sea. The site has three main coastal towns: Porto Garibaldi, Lido degli Estensi and Lido di Spina.
It is located in the Comacchio Municipality on the Po plain, to the south of the Po River Delta, the largest natural reserve in Emilia-Romagna and a UNESCO World Heritage site. The area is also included in the RAMSAR convention, includes sites of EU importance (92/43/CEE Directive) and sites for bird species protection (79/409/CEE Directive).
Porto Garibaldi-Bellocchio and its hinterland is characterised by the presence of wide lagoons, wetlands and canals. Most of the territory is extremely low-lying, with coastal elevations reaching a maximum of just 2m above MSL, and a large part of the hinterland being below sea level.
Porto Garibaldi-Bellocchio is a low-lying area, highly exposed to extreme events, in which multiple human activities co-exist (Nordstrom et al., 2015) and (Bertoni et al., 2015). Of high importance for the goal of the project, is the co-existence of a complex and exposed ecosystem with high socioeconomic stakes.
Coast and hazards
The coastal area is composed of low sandy beaches of widths ranging from 30 to 300m, south-to-north. The micro tidal regime of this area has a neap tide range of 0.3 to 0.4m and a spring tide range of 0.8 to 0.9m. The wave regime is generally of low energy, with almost 65% of wave heights being less than 1m. Energetic storms come from the east-northeast (Bora wind) and southeast (Scirocco wind). The 1-in-1 year return period wave height is 3.3m with a wave period of 7.7s (Armaroli et al., 2012).
The area can be divided into a northern and southern section of almost equal lengths. The morphological and sedimentary behaviour of these sections are substantially different. Most of the northern is advancing due to sand that travels south-to-north alongshore along the coast while the southern section is threatened by erosion. Stakeholders remark that natural areas are basically not managed and no interventions are carried out to achieve their long‐term survival. Dune trampling is a major issue in natural areas and parks are not sufficiently valued.
The northern section is mostly urbanised and the beach is characterised by the presence of bathing establishments that provide numerous services to beach users during the summer months. Two towns, Lido degli Estensi and Lido di Spina, with a total of 2,750 inhabitants, were built in this section in the 1970s and are divided by an artificial canal. Several measures like an earth embankment and walking path and barrier protect the Lido di Spina south urban areas from flooding. The northern section also includes a short stretch of natural dunes (Lido degli Estensi north).
Meanwhile, the southern section of the study area is natural and characterised by the presence of the Bellocchio marsh that is divided into two parts by an artificially-created channel which ensures water quality within the wetlands and prevents adverse effects to aquaculture and fisheries as well as to birds and biodiversity. The southern section is retreating and large overwash fans are evident in its northern part (Bertoni et al., 2015). The Reno River is at the southern boundary of the case study site. Its right bank was protected from erosion between the 1980s and 1990s by rubble mound slopes and earth embankments. In recent years however the previously visible spit has disappeared due to storm action.
Predictability
Within the current Regional Civil Protection protocol for the Emilia-Romagna coastline, three-day wave and water level forecasts are undertaken daily by the HydroMeteoClimate Service of Emilia-Romagna (ARPA-SIMC) through its meteo-marine operational forecast system (Cacciamani et al., 2012). A series of critical storm thresholds have been identified by Armaroli et al. (2012). These thresholds are as follows:
1) a combined significant wave height and sea water level of 2 m and 0.7 m respectively (thresholds for urbanised zones).
2) a combined significant wave height of 3.3 m and a sea water level (including surge and tidal effects) of 0.8 m (thresholds for natural areas with dunes).
3) a combined significant wave height and sea water level of 2 m and 0.7 m respectively (thresholds for urbanised zones).
When at least one of these thresholds is predicted to be exceeded by the wave and water-level prediction models, the HydroMeteoClimate Service issues a weather warning to the Civil Protection authority. Based on all the available information and the hazard evaluation, the authority then decides on whether or not to issue a civil protection alert. This alert is sent to local authorities and operation structures so that they can take the necessary actions indicated by their emergency plans.
Table 1: List of criteria used to define thresholds for each beach type and the chosen values. (Armaroli et al. 2012).
|
Beach type |
Storm impact |
Parameter |
Thresholds |
|---|---|---|---|
|
Natural with dunes |
Morphological change (dune erosion/destruction) |
Wave height (Hs) |
T1 wave height = 3.3 m |
|
Water Level (surge + tide) |
T1 WL = 0.85 m above MSL |
||
|
Anthropic |
Inundation and damage to infrastructures |
Wave height (Hs) |
Hs = 2.00 m |
|
Water Level (surge + tide) |
WL = 0.7 m above MSL |
An Early Warning System was created within the MICORE EU Project and is used to predict hazardous conditions for several areas along the coast (Harley et al., 2012). Alerts are issued based on two Storm Impact Indicators (SIIs) and are named Building Waterline Distance (BWD) and Safe Corridor Width (SCW). Both indicators represent the distance between a building, a tourist facility or an infrastructures (BWD) or between the dune foot (SCW) and the maximum water level forecasted as described above. If the distance is below certain pre-defined thresholds, an alert is automatically issued and is then discussed within the Functional Centre. The Functional Centre is composed of personnel from three different regional agencies – ARPA-SIMC, SGSS and Civil Protection. ARPA-SIMC provides hydro-meteo forecasts and sea state forecasts (wave height and water levels).
When a forecast is generated, the professionals discuss whether or not to issue an alert according to several criteria, such as, for coastal areas, the expected water level, the foreseen duration of the storm, the state of the coastal area (if it was already affected by antecedent storms of not), the Early Warning System outputs, etc. Once an alert is issued, all the information on likely consequences to happen is sent to local coastal Councils, Technical River Basin Services, Local Civil Protection agencies, volunteers working with Civil Protection, law-enforcement agencies (Police, Port Authorities, etc) and to all regional offices involved in coastal risk management.
Historical flood events
The coastal zone is an area of strategic importance for the Emilia-Romagna region, containing one of the largest tourist systems in all of Italy as well as being a centre for many significant industrial activities. Human pressure on the coast – particularly since the Second World War has exacerbated natural phenomena such as subsidence, beach erosion and flooding during storms, endangering both human settlements and economic activities. The sustainable management of the coast is therefore a high priority for the Emilia-Romagna Region.
Coastal storms that have affected the Emilia-Romagna coastline since 1946 have been analysed as a part of a storm catalogue initially built during the MICORE project and currently maintained by the Regione Emilia-Romagna (Perini et al., 2011). A detailed catalogue of each storm that occurred between 1946 and 2010 was created and is available for download (in Italian).
All the information on more recent events, i.e. between 2011 and 2016, are being archived by the Geological Survey of Emilia-Romagna. Furthermore, an extensive topographic survey campaign is regularly performed by the Geological Survey along profile lines that are located in vulnerable areas of the coast. The profiles are surveyed after every significant storm (i.e.: a storm that caused damage as reported by local authorities and newspapers). With regards to the above-mentioned catalogue (and the more updated 2011- present data) the information related to each event has been extracted from several sources, such as technical reports, regulations and intervention plans, photographs, newspaper articles, remotely-sensed data, hydrological records and river floods archives.
This information has been extracted from the RISC-KIT "Review report of key challenges and lessons learned from historical extreme hydro-meteorological events".
The datasets on storms are available for download from the project’s historical storm database.