The legal regime of the territory: An opportunity to defend the natural risk of a geographical space

by Rafael Martínez ¹, Jesús Mateo ²

¹  Professional Association of Geographers of Aragón, Luces de la Ciudad, 33, 50.019, Zaragoza (Spain)

²  Dept. of Earth Sciences, University of Zaragoza. Pedro Cerbuna, 12, 50.009, Zaragoza (Spain)

*  Corresponding author: rafael.martinezc@gmail.com

Abstract

Any project, plan, or program, whether public or private, implemented in a geographical space must comply with a legal framework. This legal framework varies over time for various reasons. However, it primarily varies depending on the regulations governing its use or exploitation, whether urban planning, environmental, or topical. Natural risk as an element for decision-making isn`t selected as a disruptive factor for the implementation of any productive activity. The legal framework, as a transparent layer for achieving sustainable development, must provide objective instruments that lead to harmonious development in the geographic area where any human activity is to be implemented.

The communication details the need to articulate the mandatory procedural legal elements so that the natural risk of a given geographic area is a key element for decision-making by any public or private actor. The case study focuses on the operational work of hydrological risk in small watersheds around Aragón, contrasting and analyzing existing work methodologies and legislation to detail which guidelines and recommendations should be incorporated into the current legal framework to prevent residential, secondary, or tertiary uses of the territory from being implemented in areas threatened by public safety in the face of a known natural risk.

Keywords

place spatial planning, natural hazard governance, territorial regulation, flood risk management

Note:

Papers published in this special issue of the European Geologist journal have undergone a thorough peer-review process but have not been copy-edited. Authors bear full responsibility for the linguistic accuracy of their contributions.

This work is licensed under a Creative Commons Attribution 4.0 International License.

1. Introduction

This communication presents a critique of the current legal and technical framework regarding protection against natural hazards. This critique is applicable to any geographical area in the world. The implementation of this framework is essential for carrying out any territorial plan, project, or program, whether public or private. Recognizing natural risk as a key element in the development of territorial public policies or in the implementation of private projects justified by the public interest to improve citizens’ quality of life requires a constructive technical critique in order to identify the needs within the current legal and technical systems.

Aragon has been selected as the geographical area to analyze the legal and technical requirements necessary for the territorial regulatory framework to become an opportunity to protect people and property threatened by natural risks. Natural catastrophes such as the Biescas event in 1996 (Figure 1), the Valencia disaster in 2024 (Giner Pérez de Lucia, 2025), and others reinforce the urgent need for legal and technical review so that territorial and urban-planning decisions effectively contribute to human protection against extreme natural events. Especially when considering that natural disasters, such as the one in Biescas, have been resolved through the courts, clarifying civil and political responsibilities after more than two decades of litigation. The Biescas case establishes that the existence of an extreme natural phenomenon does not exclude administrative liability when the damage is foreseeable and when the public administration allowed exposure to the risk.

Figure 1: Biescas campìng destroyed within the Arás Ephemeral stream alluvial cone. Orthophoto 1998 vs. Lithological Map by Soler Puig de Fábregas, 1958. Biescas, Huesca, Aragón. Approximate scale 1:5,000. Source: ICEARAGON.

From the standpoint of current legal and technical practice, the aim is to identify objective legal and technical premises that enable public authorities to promote the development of productive or non-productive territorial activities in areas where natural hazard levels are low or very low. This is an essential and urgent task considering that natural systems have changed due to an increase in extreme natural events driven by climate change (Fischer & Knutti, 2015). This broadens the scope of the Brundtland Report (Brundtland, 1987), whereby sustainable development is meaningful only when it considers the needs of future generations who must live on planet Earth, alongside the economic viability of any project to be implemented in a given territory.

2. Development

Aragón, with more than 47,000 km², is characterised by significant geological and physiographic diversity due to its territorial configuration. The major landscape domains—Pyrenees, pre-Pyrenean foothills, Ebro Valley, Iberian piedmont, and the Iberian Range—form a physical setting with substantial variability in natural hazards throughout the region, including landslides, rockfalls, subsidence, strong winds, river flooding, flash floods, and avalanches. The Territorial Planning Strategy of Aragón (EOTA, 2014), approved under Decree 202/2014 of 2 December, calls for the integration of natural hazards into territorial planning through prevention criteria, environmental compatibility, and natural-environment conservation in the face of natural threats. The EOTA is binding on public administrations and serves as guidance for the private sector, being mainly implemented through urban planning, territorial planning instruments, and territorial and environmental assessment procedures. One of its objectives is risk reduction through regulation and control of activities directly associated with hazard-triggering processes.

To this end, Objective 20 aims to improve knowledge of natural and induced hazards and reduce their effects by preparing and revising hazard and susceptibility maps; and by developing a Special Guideline on Natural and Induced Hazards to define land uses and prevention or mitigation measures according to susceptibility levels. Urban-planning instruments must integrate hazard criteria: guiding development toward low-risk areas, avoiding new risk generation, applying the precautionary principle, excluding high-susceptibility areas from urbanisation, and designating critical areas as protected non-developable land. Hazard maps must ultimately be incorporated into territorial and urban-planning instruments.

In practice, a decade later, the development of these objectives has had limited or negligible reach because their implementation depends on multiple public bodies that must be coordinated and territorially supervised. The empirical evidence is that the EOTA has not implemented real monitoring of the compliance with the objectives, strategies, and regulations established in the Decree. It´s therefore essential to adopt practical technical actions that allow the current territorial legal framework to become a genuine opportunity to protect Aragón’s population and productive activities from existing natural hazards. This regulatory framework must account for public policies on urban planning, territorial and environmental planning, topical regulations, environmental assessment, and construction standards applied to territorial plans, programmes, and projects. Proper strategic planning and assessment will improve civil-protection plans, particularly in view of the increasing recurrence of extreme natural events.

The foundational legal requirement involves enforcing EOTA Objective 20 by the administrative unit responsible for hazard mapping and developing the corresponding Special Guideline on Natural and Induced Hazards. This objective has not been carried out to date. This prevents Natural Risk from becoming a mandatory criterion within the urban, environmental, or sectoral planning of any project, plan, or program. In parallel, the Government of Aragón should draft a Special Guideline on Territorial Suitability and Capacity to regulate the deployment of productive economic activities, particularly on developable land and on general non-developable land where a large proportion of topical, non-residential territorial projects—such as energy-evacuation lines, transformer centres, and industrial facilities—are located. Existing special guidelines (e.g., livestock operations, landscape planning in the Matarraña/Matarranya region) illustrate the potential of these instruments.

Returning to the case study addressed in this communication—extreme flash-flood hazards such as the Arás Ephemeral stream (Biescas) in mountain environment, the “Barranco de la Muerte” in Zaragoza, the lateral gullies of the Cámaras River (Figure 2) and those along the lower Huerva River (Figure 3) third last examples in semi-arid or arid environments, —several lines of work can be proposed to improve the territorial regulatory framework. The aim is to avoid increasing hazard levels for residential and productive settlements. This increase is not attributable solely to urban development, but also to large strategic projects with significant territorial impact, such as transportation infrastructures and logistics platforms.

These disaster scenarios provide geographic, geological, and lithological evidence, supported by statistical and cartographic high-risk indicators that must be incorporated into hazard mapping and territorial development decisions. In the case of flash floods (Mateo et al., 2016), estimating maximum peak flows for various return periods is critical for flood-risk management, hydraulic-infrastructure design, and territorial planning.

Figure 2: Fieldwork. Damage to a retirement-home building under construction caused by flooding of the Cámaras River in Azuara, Zaragoza. June 2025. Photo: Rafael Martínez Cebolla.

In Aragón, many small to medium-sized catchments exhibit strong hydrological and rainfall variability. Traditional flood-frequency analysis based solely on gauged discharge series may be insufficient, especially when records are short or unrepresentative of extreme events (Hadadin, 2013; Millán, 2014; Vittal et al., 2015). It is necessary to combine statistical methods with hydrometeorological modelling (Rainfall–Runoff–Routing, RRR models) to obtain more realistic flood-frequency estimates. As with any frequency analysis, uncertainty increases when observed series are scarce or non-representative. Simplified hydrological models, while useful, may fail to capture key nonlinear processes, spatial–temporal variability, and saturation effects, suggesting the need to combine methodologies in detailed engineering and civil-works studies.

Figure 3: Lateral Ephemeral stream of La Muela (west) and La Plana (east) along the lower Huerva River. Orthophoto 2024 vs. Peña’s Geomorphological Map 2002. Approx. scale 1:50,000. Source: ICEARAGON.

Given these catchment-specific challenges, a series of technical recommendations is proposed to enhance the application of the territorial legal framework for protecting people and property, independent of any necessary legal or technical modifications to existing urban-planning instruments and self-protection measures for citizens and assets.

The first mandatory technical requirement concerns the need for high-quality, precise natural-hazard information for territorial projects. This requires hazard-susceptibility maps at 1:10,000 scale and detailed hazard assessments at 1:5,000 scale. Such mapping would resolve current deficiencies arising from low-resolution studies (≥1:50,000), which limit their practical application in planning, engineering, construction, and environmental-impact assessments.

The second requirement is the revision of construction and civil-engineering standards for infrastructures or buildings whose hydrological modelling fails to reflect real flash-flood behaviour. Linear-reservoir models, although widely used due to simplicity and computational efficiency, cannot adequately represent the complexity and temporal variability of real hydrological processes, especially during rapid-onset flood events (Mateo, 2015). One of the greatest advantages of parallel linear reservoir models is that their parameters can be calibrated with real-world events, although logically only for gauged catchments. Nevertheless, these models and their water balances allow very precise investigation of what happens in basins during extreme events. It is also noteworthy that parallel linear reservoir models, when combined, are very effective at describing all the hydrological processes involved that are of a nonlinear nature and therefore highly complex. Revising construction standards to incorporate parallel-reservoir configurations would enhance model fidelity while retaining conceptual simplicity and operational usability.

The third requirement is revising the technical-validation workflow of Environmental Impact Assessments (EIAs). The natural-risk component of many EIAs lacks the necessary technical quality for proper project siting and environmental sustainability. EIAs typically lack a true multi-hazard baseline, integrating only fragmented sectoral maps without methodological rigour. This results in impact assessments considering only hazard intensity—ignoring vulnerability—and thus producing incomplete risk evaluations. Interaction between hazard types is rarely analysed, and low-probability/high-impact scenarios are often excluded. The problem is systemic and not merely attributable to individual consultants.

Thus, validation of key EIA inputs—natural risk and socio-economic risk—must be conducted by an independent auditor rather than the project proponent. In public projects, the EIA should be drafted entirely by an external body to ensure objectivity. This guarantees environmental sustainability beyond the socio-economic benefits used to justify territorial projects.

Given the significant effort by Aragón’s public administrations in developing protection plans and risk maps (e.g., POCTEFA ALERT Project, 2023), extreme natural events remain central to territorial policy. Susceptibility zonation enables minimising catastrophic consequences and enhancing societal resilience (Varas et al., 2025). Economic justification is well established: public expenditure on repairing or defending infrastructures and facilities is substantial (Koks et al., 2019), and international organisations such as the OECD highlight the significant economic and social damage of natural disasters (OECD, 2018). The fourth requirement is therefore the creation of a public database documenting direct and indirect disaster losses—business interruption, income loss, secondary economic effects—to support informed decision-making by both public authorities and private actors. Such data would also support judicial processes addressing compensation and shared liability.

3. Conclusions

Recent experience and scientific studies demonstrate the need for a series of legal and technical measures that directly benefit society by improving defence capacity, resilience, and self-protection against increasingly frequent and severe natural hazards. Technical and legal proposals are outlined to achieve a real improvement in the environmental assessment of plans, projects, and programs with territorial impacts. It focuses on the evaluation of natural risk as a key input for carrying out any public or private action within a geographical area. Public authorities must adopt relatively low-effort regulatory modifications (decrees, regulations, standards) without requiring major legislative reform, thereby reducing administrative costs, improving efficiency and effectiveness, and—above all—protecting the population inhabiting a given geographical area. At the same time, technical improvements are needed in EIAs and construction standards to ensure that hydrological modelling reflects real conditions so that the actual risk of a given geographical space can be objectively assessed.

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This article has been published in European Geologist journal 61 – 5th IPGC Special Edition 2