Abstract
The Port of Machico, located on the Madeira Island, is an important infrastructure for the local economy and serves as a gateway for various commercial activities. However, the port is prone to overtopping events, which can result in damage to the infrastructure, disruption of activities, and harm to the environment. Therefore, it is necessary to evaluate the consequences of overtopping and identify measures that can reduce the impact of these events. The methodology proposed in this chapter uses the analytic hierarchy process (AHP) to evaluate the impact of overtopping events at the Port of Machico. The AHP is a multicriteria decision-making tool that allows the evaluation of alternatives based on a set of criteria and their respective weights. In this case, the criteria are related to the consequences of overtopping, such as economic losses, environmental impacts, and disruption of activities. The results obtained from the AHP can then be used to identify measures that can reduce the impact of overtopping, such as the construction of protective structures.
TopIntroduction
A small sheltered port with a capacity for 80 small to medium-sized vessels, with a limit of twelve tons, was built in the bay of Machico city, located on the east coast of Madeira. It is situated between two Sites of Community Importance, namely, the Pico do Facho SCI and the Machico-Queimada SCI. There is also the more recent Madeira SCI that covers all coastal marine waters around the islands of the archipelago, the Cetaceans SCI (CMM, 2022). The port is highly relevant to Machico in terms of socio-economic importance due to the local fishing activity and its function as a shelter for the bay. According to Figure 1, the port of Machico is located in a highly exposed area of the Machico bay.
Figure 1. Location of the Port of Machico
In situations of strong maritime agitation, the occurrence of overtopping in the port of Machico is very frequent, especially in the area of the main breakwater. In the port of Machico, according to data collected by the Regional Secretariat for Social Equipment (SRES), maritime agitation off Machico is observed (Table 1).
Table 1. Maritime agitation off Machico
| Madeira Island (South Coast) |
| Return Period (Years) | Seaward Maritime Agitation
Extreme Hs Values in Meters |
| SW | S | SE |
| 10 | 5,1 | 4,9 | 3 |
| 25 | 5,6 | 5,7 | 3,4 |
| 50 | 6,1 | 6,4 | 3,8 |
| 100 | 6,5 | 7 | 4,1 |
Source: SRES (2007)
Among the values, it is noted that in the port of Machico the maritime agitation for a return period of 100 years, in the South direction, reaches the maximum value of 7 m. It is also known that southwest values are not very frequent, but when they appear, if the visible extension in Figure 2 did not exist, the sheltered area would be in vulnerable conditions (Freitas, 2020).
Key Terms in this Chapter
Analytic Hierarchy Process: The Analytic Hierarchy Process (AHP) is a decision-making method developed by Thomas Saaty in the 1970s. It is a structured approach to making complex decisions, based on breaking down a problem into smaller parts and comparing them pairwise to determine their relative importance. AHP involves creating a hierarchy of decision criteria and alternatives, and then comparing them using a series of pairwise comparisons to determine their relative priorities. This process results in a numerical weight or priority for each criterion or alternative, which can be used to make a final decision. AHP has been widely used in fields such as engineering, management, and environmental sciences for a variety of decision-making applications.
Port: A port is a facility where ships can load and unload cargo or passengers. Ports can be found in coastal areas, along rivers or lakes, and they play a crucial role in global trade and transportation. Ports can have various types of infrastructure, including docks, wharves, piers, and terminals, as well as cranes, containers, and other equipment for handling cargo. They can also provide services such as customs clearance, storage, and maintenance for ships.
Madeira: Madeira is an autonomous region of Portugal located in the Atlantic Ocean, southwest of the portuguese mainland. It is an archipelago composed of two inhabited islands, Madeira and Porto Santo, and several uninhabited islands and islets. The region has a subtropical climate, with mild temperatures throughout the year, and is known for its beautiful landscapes, including mountains, forests, and coastlines. The economy of Madeira relies heavily on tourism, as well as agriculture and fisheries.
Overtopping: Overtopping is a coastal engineering term that refers to the phenomenon of waves breaking over a barrier, such as a seawall, and flowing onto the landward side. This can lead to flooding, erosion, and damage to infrastructure and property. Overtopping is typically quantified in terms of volume or discharge rate, and is influenced by factors such as wave height, wave period, and the elevation and roughness of the barrier. Overtopping can be managed through the design of coastal structures, such as breakwaters and revetments, that are intended to reduce wave energy and prevent or minimize overtopping.
Machico: Machico is a city located on the eastern coast of the island of Madeira, which is an autonomous region of Portugal. It is known for its historical importance as the landing site of the discoverers of Madeira in the 15th century, and for its beautiful beaches and natural landscapes. The city has a population of around 20,000 people and is an important commercial and tourist center on the island.