Modeling of Flood Risk: Vulnerability and Adaptation of Machico City Center

Introduction

Alluvial processes and floods are natural phenomena that are increasingly subject to human influence and interference. Throughout history, human beings have adapted land distribution and usage to reduce exposure and vulnerability to local alluvial patterns. However, there has recently been a significant increase in exposure to risk factors due to inadequate planning in relation to local realities. In this context, a case study was carried out in the Machico River basin in Portugal, which included:

• 1.

  Hydrological modeling of the basin, calculation of peak flow, flow modeling, calculation of runoff surface, and flood areas for different return periods;

• 2.

  Description and characterization of flood history, identification, inventory, and characterization of exposed elements, as well as research of property owners and residents for vulnerability analysis of the historical center of Machico in flood situations;

• 3.

  Evaluation of the degree of land use adaptation to flood occurrence in relation to spatial and environmental planning options.

The size and diversity of conditions, along with changes in land occupation and usage in river basins, lead to floods in riverside areas, where the main regional and local urban centers are usually located. Alluvial processes expose a range of natural and human heritage elements, including the built and cultural heritage of Machico's historical zone (Alves et al., 2022b). These more vulnerable spaces require greater knowledge, organization, and training, reflected in municipal planning and licensing options, as well as in the planning and management of classified and protected environmental spaces, in order to anticipate, manage, and recover from alluvial/flood events. Technological instruments, particularly geographic information systems (GIS), can be central elements in describing, evaluating, and supporting risk management, implementing collaborative risk governance systems at regional and local scales, and managing territorial risks, particularly those related to floods.

Flood risk management is essential to ensure the safety and well-being of populations, protect the environment, and sustain economic development. Goal 13 of the UN's 2030 Agenda highlights the importance of adaptation and resilience measures to address challenges related to climate change and minimize the impact of natural disasters such as floods (RSENR, 2022).

The Risk Of Alluvial Processes And Flood Areas

Considering the complexity of territorial systems, it is important to implement an evaluation of the possible harmful consequences of future floods for human health, the environment, cultural heritage, and economic activities. This evaluation should take into account issues such as topography, the position of watercourses and their general hydrological and geomorphological characteristics, the location of populated areas and economic activities, and long-term evolution, including the impacts of climate change on flood occurrences, as foreseen in Directive 2007/60/EC of 23 October, transposed into national legislation through Decree-Law No. 115/2010 of 22 October (Directive on the Assessment and Management of Flood Risks).

Through Directive 2007/60/EC of the European Parliament and of the Council, of 23 October 2007, a framework was established for the assessment and management of flood risks, in order to reduce the consequences associated with floods that are harmful to human health, the environment, cultural heritage, and economic activities. This directive was transposed into domestic law through Decree-Law No. 115/2010 of 22 October, thus establishing a framework for the assessment and management of flood risks.

The scope of Directive No. 2007/60/EC defines flooding as “the temporary covering by water of land which is normally not covered by water. It includes floods resulting from rivers, mountain torrents, and ephemeral Mediterranean watercourses, and floods resulting from the sea in coastal areas, and may exclude floods originating from sewerage systems.”