From Waterpower to Fragility: Analysis of Historic Watermills in the Aterno Valley for Risk Assessment and Sustainable Development

Abstract

The interaction between humans and water has historically shaped landscapes, in which rivers played a central role in the development of territories. Among the infrastructures developed to manage water resources, watermills had always represented a key element of minor cultural heritage, reflecting centuries of adaptation to environmental, economic, and technological conditions. Although once central to river landscapes, these structures are now largely forgotten and at risk of being lost, particularly in Italy’s inner areas affected by rural depopulation, climate change, and natural hazards. The case analyzed in this paper, part of a larger research project, focuses on the analysis of watermills in the Aterno River valley in the Abruzzo region of central Italy. This fragile mountainous area is currently threatened by natural hazards and depopulation. The aim is to fill the gap in documentation on this “minor heritage,” which has been identified and cataloged, along a timeline of its vulnerabilities, starting from historical cartography, integrated with a localized field survey within a geographic information system. The GIS facilitates the cross-referencing of historical, geospatial, and environmental data, including hydrogeological and flood risk information. The results demonstrate how water, once a resource, has become a vulnerability factor and highlights the fragility of these historic artifacts, contextualized within the surrounding landscape.

1. Introduction

River landscapes, layered over time, represent complex ecosystems that preserve environmental and cultural values closely linked to the interaction between humans and water [1,2]. In these complex contexts, water is the central element, both as a source of survival and as a socio-cultural attraction, since its availability or lack thereof has been and still is a decisive factor in the construction and transformation of the landscape, in which material and immaterial aspects merge in an inseparable relationship [3].

In fact, from ancient times to the present day, man has shaped the river landscape by building fords, bridges, irrigation canals and mills. Among these objects, created to tame or exploit the presence of the river, water mills, more or less preserved and recognizable, are a significant testimony to the built landscape and the transformations that reflect historical evolution, in response to the economic and productive needs of the people of the past [4,5,6,7]. Although these structures were of great importance because they characterized entire river landscapes, spreading throughout areas defined by the presence of rivers, today they are considered part of the minor heritage, i.e., not monumental, which needs to be analyzed, interpreted, protected and returned to the community before its memory is lost altogether [8,9,10,11].

Knowledge and documentation of water-powered mills and related technological systems allow us to explore important environmental and economic issues and rediscover ancient technological knowledge that enabled water to be used as a driving force, as well as to understand the reasons that led to their decommissioning and abandonment, in line with the objectives set out in Agenda 2030 [12,13,14]. This Agenda is a plan drawn up in 2015 by all United Nations member states to guide actions toward achieving 17 goals in areas considered crucial for humanity and the planet.

It is therefore interesting to evaluate the current possibilities for the regeneration of river landscapes, identifying watercourses, once a key element of territorial development, as the backbone of ecological, economic, social and cultural networks, seeking to reconnect, through an in-depth process of knowledge, the historical dimension with the contemporary one [15].

Water, which in the past was a necessary resource for powering mills and was therefore canalized and utilized, is now a factor that must be monitored for abundance and/or scarcity, both of which can pose risks. This issue becomes even more relevant in the context of the challenges posed by the climate crisis, which alternates periods of drought with extreme events of intense precipitation, and in relation to the transformation of rural contexts, often subject to abandonment linked to the depopulation of the Italian inner areas [16,17]. For these reasons, knowledge of water mills and the surrounding river landscapes is part of a broader and more current reflection on the need to identify models of development, regeneration and enhancement capable of interacting with anthropized territories and new usage requirements [18].

This research challenge is even more pressing in fragile territorial contexts, where natural risks, such as frequent seismic activity, climate change and hydrogeological instability, threaten the physical preservation of artifacts, leading to the physical loss of assets. This is accompanied by a gradual disappearance of the historical memory of the activities, knowledge and relationships that have shaped what we can now define as ‘cultural landscape’ [19]. In this regard, the issue of democratic participation in the knowledge and enhancement of heritage appears to be topical, with a view to understanding, communicating, preserving and passing on this legacy to future generations, teaching local communities to recognize the cultural value of such artifacts, and hoping for the emergence of what the Faro Convention [20] calls heritage communities [21,22].

This is the background for the research project called Multilevel Application for Cultural Information Archives (M.A.C.IN.A.). A focus on the Inner Areas of Abruzzo and Sardinia regions, funded by the PRIN 2022 PNRR program, aims to explore the minor heritage of watermills in the Abruzzo and Sardinia regions through an interdisciplinary research approach [23]. The research aims to integrate the digital representation of geospatial and architectural data relating to water mills in these two Italian regions. The data, collected with particular attention to the diachronic reading of historical transformations of the landscape (Heritage/Historical GIS) and those of its built heritage (Heritage/Historical BIM), is integrated with data from the analysis of hydrogeological and hydroclimatic time series. This integration aims to understand the complex cause–effect mechanisms that have led to the current evolution of the areas analyzed and to create the conditions for implementing a multi-scale information model of the landscape and the built heritage within it.

This multiscale platform, which derives from the integration of diachronic spatial and geographical information at the territorial scale (HGIS) with architectural-scale information about the material consistence and evolution of the mills under investigation (HBIM), aims to be a complex, multilevel information management tool, Heritage/Historical Landscape Information Modeling (HLIM), which represents the final output of the M.A.C.IN.A. research project.

To this end, the project intends to develop outputs aimed at communication and heritage education to ensure the resilience of sites and their sustainability through participatory processes aimed at the involvement of civil society. The transdisciplinary expertise of the research teams involved in the project ensures that the theme of the human–landscape relationship is addressed from a multi-objective perspective supporting the development and sustainable conservation of marginal and little-known territories, specifically those located in the inner areas of the Abruzzo and Sardinia regions.

This paper describes the results of the initial steps of the M.A.C.IN.A. research project, in which considerable data are collected on a territorial scale and analyzed in relation to the risks to which the area is exposed, using territorial graphic representation tools [24,25]. The combined use of historical maps, orthophotos, data acquired through thematic field analysis and risk maps within a geographic information system (GIS) environment enables risk analysis and the organization of collected data in a format that can serve as a knowledge tool for the recovery of built assets and the promotion of sustainable territorial development. This is made possible by creating a specific database derived from projecting historical data onto a georeferenced base, followed by operations that enable attributes to be transferred from one information layer to another via spatial joint processing.

This is the main context for the research presented here, which aims to analyze the hydraulic mills located in the inner Abruzzo area, a mostly mountainous region of central Italy that represents a particularly present topic, based on recent scientific literature [26,27,28,29]. This geographic area is characterized by limestone massifs with high peaks that have ensured an abundance of water over time [30]. Its spread throughout the territory through rivers and streams has encouraged the use of water as a driving force and therefore as a renewable energy resource. Starting from these premises, the work presented aims to deepen our understanding of the network of hydraulic mills distributed along the Aterno River valley, in the province of L’Aquila.

The paper is divided into four sections: “Materials and Methods,” which frames the study area in relation to the territorial framework and historic context and describes in detail the methodological approach adopted; “Analysis and census of hydraulic structures in the Aterno Valley,” which presents the work carried out on the mills of the Aterno Valley for their rediscovery and classification; “Watermills and risks: data interpretation and visualization in a GIS environment”, which discusses the results of the research; and the “Conclusions” section, which reflects on how the data produced can support the management of minor heritage, promoting strategies of re-functionalization and promotion through sustainable tourism, cultural regeneration and valorization.

2. Materials and Methods

The research employs an integrated and interdisciplinary approach, combining research on edited documents with field surveys and interpretation and visualization of data in a GIS environment. The aim is to assess the past role and future potential of hydraulic mills in the Aterno Valley, paying particular attention to the knowledge of material and immaterial values, and then to analyze the risk factors that plague this heritage, from the hydrogeological to the abandonment and the memory loss of these artifacts with cultural value.

Rediscovery and value attribution have the potential to create a shared knowledge system that can support the definition of future strategies and the design of actions for the sustainable fruition and enhancement of this minor heritage.

2.1. Territorial Framework

The Aterno–Pescara River is the most significant of its kind in Abruzzo, stretching approximately 150 km with a hydrographic basin that extends into the provinces of L’Aquila and Pescara (Figure 1). This river originates as the Aterno from the Laga Mountains and flows through the territory of the province of L’Aquila, collecting the waters of numerous tributaries, such as the Vetoio, Raio, Vera and Sagittario [31]. At the height of the municipality of Popoli, the Aterno joins the Pescara River, which, collecting the waters of the Tirino, Giardino and Orta rivers, flows into the Adriatic Sea [32].

The Aterno River has historically played a strategic role in the settlement and economic development of the territories it flows through, serving as vital natural infrastructure that supports local economies [33,34]. The water of the river and its tributaries supported a wide system of activities related to agriculture, animal husbandry and production. The construction of buildings to produce handicrafts and food led to the development of the built landscape, which is direct evidence of the close relationship between people and the environment based on the sustainable use of water resources. This historical balance has been lost over time due to repeated human activities, excessive land use, intensive agricultural practices, and related phenomena that have also contributed to a progressive deterioration of the river’s ecological status [35].

This territory, like many of those defined as Internal Areas [36], has been affected by forms of depopulation that have led to the abandonment of parts of villages [37] but also of rural areas and minor built heritage. This is also reflected in the conservation of artifacts and ecosystems.

Waterways in general, and rivers in particular, are among the most globally threatened ecosystems, encountering numerous hazards and risks [38]. In this context, it is essential to reconsider the relationship between the communities of the Aterno Valley and the river that flows through it, moving beyond a purely functional or marginal perspective.

The implementation of the Aterno River Contract [31,39,40] represents a significant step in this direction, aligning with the similar River Contracts recognized in Italy by Legislative Decree 152/2006 [41]. However, these processes still do not constitute territorial planning tools [42] that foster the development of integrated and collaborative management models for the river system [43,44,45,46], proposing strategies aimed at the resilient conservation of river ecosystems [47]. Nevertheless, despite the innovative foundations and growing interest in this approach, numerous challenges remain, including limited up-to-date knowledge about the hydraulic structures present in the river valley. These limitations underscore the need to strengthen active community involvement, fostering a renewed river culture grounded in comprehension, heritage enhancement, and the sustainable regeneration of the river landscape [48].

In this perspective, the historical interaction between humans and the natural landscape takes on central importance, and the study of the spread of historic water-powered structure, such as sawmills, fulling mills, copper mills, and, above all, water-powered mills, along the course of the river and its main tributaries can add value to the design of cultural and environmental regeneration projects in the area. These structures, now largely unknown, abandoned, or difficult to access, represent a significant component of the cultural landscape along the river, testimony to the productive and agricultural memory of local communities in past centuries [11]. Their presence highlights the strategic role of a production network, which, by using the power of water, helped shape the environmental landscape through the construction of structures and infrastructure for the diversion and discharge of specially canalized water. In the current context marked by climate change, water, which was once a central energy resource, presents a double problem: some structures are increasingly lacking water in their diversion channels due to the fragmentation of the canal network and prolonged seasonal drought, while other structures are in areas at risk of flooding following heavy rainfall.

This transformation of the relationship between mills and rivers, from energy resource to element of vulnerability, requires in-depth knowledge and reinterpretation of the hydraulic heritage, both historically and in the present day, to understand how mills and rivers can be reintegrated into land management, including through culturally based regeneration strategies involving local communities.

2.2. Methodological Approach

The methodology used for analyzing the watermills in the Aterno River valley involves a combination of diverse methods and approaches. This process begins with data collection, which is divided into several phases, and continues with interpretation into a GIS environment (Figure 2). This approach enhances understanding of single structures, assessing them both from a typological–formal conservation perspective. Additionally, it considers the landscape and environmental context in which they are located, with a particular focus on their relationship with water.

The first phase of the workflow involved a critical review of the state of the art about hydraulic mills located in the Abruzzo region, particularly in the L’Aquila area, to extract usable data for increasing knowledge of these water-related structures. To investigate the distribution of hydraulic mills in the area, this study analyzes the available technical cartography. The analysis draws on 1:25,000-scale topographic maps produced by Italian Organization ‘Istituto Geografico Militare’ (IGM). This is a technical map that has historical value as it depicts many artifacts of cultural significance. This Institute started producing maps in the 19th century and continued in paper form throughout the 20th century. Historically, the Institute divided these maps into sheets, known as ‘tavolette’, each covering an area of approximately 6′ × 6′.

It also depicts contour lines at 25 m intervals. Historically, maps were projected using the Universal Transverse Mercator (UTM) system, with the ED50 geodetic reference system applied to the 25 series and ETRS89/GRS80 adopted for the 25DB series, introduced in the early 2000s [49]. Although traditional map production was suspended in 2014, a new generation of digital maps—the 25DBSN series—was introduced in 2022. These maps are generated through automated production processes and are continuously updated using territorial databases. They are distributed under the Open Data Commons Open Database License (ODbL), version 1.0. The current reference system in use is RDN2008/Italy Zone E-N, EPSG:7794 [50,51,52,53,54,55].

The widespread diffusion of IGM cartography throughout Italy makes it possible to replicate the process presented in this paper in other geographical contexts characterized by widespread presence of historic water-powered mills. This assertion is supported by similar studies that have incorporated IGM cartography among their sources for the analysis of mills [9,56,57,58].

The IGM cartography provides a detailed representation of natural and anthropogenic features, including waterways, hydrography and orography, transport networks and, above all, urban and rural settlements such as dwellings, farms, towers, churches, fountains and caves. In this way, the methodology proposed can be applied to other types of artifacts that are no longer in use or are poorly known, distributed throughout rural areas of Italy, to increase awareness and preserve their memory, as demonstrated by similar works [59,60,61].

The data collection and acquisition phase continued with field surveys aimed at validating the previously gathered information and enriching it through the compilation of a quick form, structured according to the standards established by the Italian Central Institute for Cataloguing and Documentation (ICCD) [62,63]. The cataloging process adopted a controlled vocabulary to ensure terminological consistency by ICCD guidelines and incorporated the rural architecture cataloging form based on ArCo ontologies [64,65].

The second phase of the methodological workflow focused on data interpretation through the development of a GIS project using the open-source QGIS platform. This project enabled the cross-referencing and interpretation of minor built heritage located along the Aterno River and its main tributaries. The analysis was conducted overlapping several maps, such as OpenStreetMap (OSM) cartography, onto which raster layers—accessed via Web Map Service (WMS) from the Abruzzo Region Geoportal—were reprojected [66]. This process enabled the digitization of the watermills through the creation of point entities, each of which was associated with a unique ID. In a subsequent step, the structures previously identified with point entities were represented with polygonal elements with explicit reference to the polygonal geometries of the buildings identified by the Regional Technical Map of the Abruzzo Region (CTR) on a scale of 1:5000. The CTR is part of the open data made available by the regional government without copyright restrictions. Everything necessary for the project was then transferred to a geodatabase with the ETRS89 geodetic reference system, which fully overlaps with the CTR layers [67]. Finally, a specific information set was implemented for each entity, linking the CSV file exported from the database.

To enhance the information base, the geodatabase was also interfaced with the Digital Surface Model (DSM) provided by the National Geoportal of the Ministry of the Environment and Energy Security. This dataset [68] includes the DSM FIRST, a high-resolution (1 m) digital surface model derived from LiDAR scanning conducted via an aerial platform, acquired by the Ministry as part of the Extraordinary Environmental Remote Sensing Plan.

In parallel, an overlay was created using orthophotos—also part of the open data released by the regional government—which consist of aerial imagery captured during survey campaigns conducted between 1982 and 2019 (

Table 1. Summary table with specifications of the orthophotos used (data reworked from [69]).

Name	Layer Name	Flight Year	Description	Pixel Size/Spatial Resolution	License
Orthophoto 1982–1986	Mosaici_UTM-WGS84_RA_82-86	1982–1986	Orthophoto created from scans of negatives produced during the 1982–1986 flight over the Abruzzo region	Low quality, no further details have been provided	Abruzzo Region (CC BY-NC 3.0).
Orthophoto 1997	Mosaici_UTM-WGS84_1997_AGEA	1997	Orthophoto taken in 1997 by AIMA, the state agency for agricultural affairs, now replaced by AGEA.	Spatial resolution from 1:10,000 to 1:25,000	Abruzzo Region (CC BY-NC 3.0).
Orthophoto 2000	Mosaici_UTM-WGS84_2000_CGR	2000	Orthophoto elaborated by ERDAS APOLLO Essentials 2015.	Spatial resolution 1:10,000	Abruzzo Region (CC BY-NC 3.0).
Orthophoto 2001–2005	Mosaici_UTM-WGS84_2001_RA	2001–2005	Orthophoto created by processing photographs taken during two separate flights. Digital orthorectification based on a digital model with a regular grid of ground coordinates measuring 40 × 40 m produced an orthorectified and georeferenced image.	Pixel size 0.50 × 0.50 m	Abruzzo Region (CC BY-NC 3.0).
Orthophoto 2007	Mosaici_UTM-WGS84_abruzzo07_WGS84	2007	Orthophoto derived from digital photos with a resolution of 12 microns taken during flights over the Abruzzo region between June and October 2007. Digital orthorectification was performed based on a digital model with a regular grid of ground coordinates measuring 10 × 10 m, producing an orthorectified and georeferenced image.	Pixel size 0.20 × 0.20 m	Abruzzo Region (CC BY-NC 3.0).
Orthophoto 2009	Mosaici_UTM-WGS84_OrtofotoPostSisma_WGS84.ecw	2009	Orthophoto created by AGEA from a flight carried out on 8 April 2009, over the municipality of L’Aquila to view the state of the areas affected by the earthquake after the catastrophic events of 6 April 2009	Pixel size 0.20 × 0.20 m	Abruzzo Region (CC BY-NC 3.0).
Orthophoto 2009_Oct.	Mosaici_UTM-WGS84_Orto2009_AGEA	2009	Orthophoto of the province of Chieti and part of the province of L’Aquila, particularly the areas affected by the 2009 earthquake. The orthophoto was created by processing photographs taken during a flight over the area of the so-called seismic crater in October 2009.	Pixel size 0.20 × 0.20 m	Abruzzo Region (CC BY-NC 3.0).
Orthophoto 2010	Mosaici_UTM-WGS84_Orto2010_AGEA	2010	Orthophoto of the provinces of L’Aquila, Pescara, and Teramo obtained from the processing of photographs by aircraft equipped with digital cameras.	Pixel size 0.20 × 0.20 m	Abruzzo Region (CC BY-NC 3.0).
Orthophoto 2018–2019	Mosaici_UTM-WGS84_2018_2019_Regione_Abruzzo	2018–2019	Orthophoto derives from digital photos taken during flights over the Abruzzo region. Digital orthorectification was performed based on a digital model with a regular grid of ground coordinates measuring 10 × 10 m, producing an orthorectified and georeferenced image	Pixel size 0.20 × 0.20 m	Abruzzo Region (CC BY-NC 3.0).

).

Data collection has been expanded to include landscape and environmental aspects through consultation of risk derived from the Abruzzo Region’s flood defense plan (PSDA), as well as risk maps derived from the hydrogeological plan (PAI). The former is a planning tool that aims to reduce flood risk in specific areas, such as those near watercourses, while the latter aims to reduce hydrogeological risk by identifying areas at risk of landslides, erosion, and other water-related phenomena. Both plans categorize areas at risk on a scale from 1 (minimum risk) to 4 (maximum risk).

This approach allowed for an overall understanding of the phenomena that affected the area under study and their consequences on structures, such as the abandonment or compromise of sites due to excess or lack of water. The issue of preserving the environment and historical built heritage is very relevant in Italy [70]. Among the tools used by legislators is the creation of protected areas, i.e., areas of the territory where there is strong protection of both the natural landscape and historical buildings. Therefore, as part of the research, a cross-reading of the data relating to the presence of protected areas of both national and regional interest in the territory was carried out [66].

The national diffusion of the cartographic base used for this work, such as IGM cartography and regional defense plans, allows the methodology to be replicated in other territorial contexts and applied to different culturally valuable artifacts, such as historic farms, fountains, and churches, which are not well known, to increase awareness and ensure their preservation and conservation.

Maps depicting historical features are widely available in many other countries. Several studies have been conducted over time that use historical maps and orthophotos to classify and assess the vulnerabilities of specific elements of cultural heritage [71]. Therefore, with only a few adjustments, the methodology described in this article can easily be extended to contexts other than Italy.

3. Analysis and Census of Hydraulic Structures in the Aterno Valley

The research began with an analysis of published books on the topic of watermills, aiming to find information useful for understanding the historical and current role of these structures in the context of the Abruzzo region [72].

The analyzed research highlights aspects related to technology, construction, and relations with the territory. Among the main contributions are the studies conducted in the Tavo-Saline valley, in the Loreto Aprutino area [73], in the Teramo area [74], in the Majella piedmont [75], and in the L’Aquila area [76,77]. This research analyses the dynamics of the milling sector in mountain villages, providing deeper insights into the technologies used by the mills.

Interest in this type of built heritage can also be found at the national and international levels, as demonstrated by the emergence of numerous associations that promote awareness and preservation. At the international level, the International Molinological Society (TIMS), founded in 1965, aims to promote knowledge of windmills, watermills, and animal-powered mills on a global scale [78]. In Italy, the Association of Friends of Historic Mills (AIAMS), founded in 2011, brings together scholars, owners, and enthusiasts with the aim of cataloging historic mills, promoting them for tourism purposes, and preserving their historical value [79]. In Abruzzo, as early as 1998, the creation of an ‘industrial archeology park’ in Pettorano sul Gizio was proposed [75] and, thanks to the efforts of citizens and scholars, it is now possible to follow a cultural tourist route that winds its way through the ancient water mills of the province of Teramo [80]. However, the census of these structures is not complete for all Italian areas, as evidenced by the poor representation of the Abruzzo region in the TIMS database, where only one mill is registered. This data highlights the need to fill a gap in the documentation and promotion of this heritage, reinforcing the validity of this research.

This premise focuses on identifying the structures using IGM cartography by recognizing buildings marked with the wheel symbol, which indicates hydraulic power structures (Figure 3). Analysis of the IGM of the Aterno river basin allowed for the identification of 64 watermills distributed along the course of the river and its main tributaries.

For each structure, a field verification process has been initiated, involving on-site surveys to confirm its presence, validate its geographical coordinates, and assess its conservation status. This activity was accompanied by a census form defined according to interoperability criteria, capable of generating a relational database constructed using tables interconnected by unique codes. This quick form, which is part of a broader research project already discussed elsewhere [81,82], was designed to ensure semantic consistency and data traceability, facilitating processing and cross-analysis in a GIS environment.

During this phase, general administrative, typological, and conservation data related to the building were collected. The information acquired concerns, on the one hand, the location, name, identification code, geographical coordinates, and level of accessibility, and, on the other hand, the architectural configuration (building type, materials, construction techniques), the original function (type of mill, presence of pipes, arches, machinery, and associated hydraulic systems), the current state (masonry structure, landscape context, accessibility), and the state of conservation (degree of integrity, degradation phenomena, and significant modifications). This information, collected via the quick form, which may seem marginal to the research presented, allows artifacts to be accurately classified and represented using three-dimensional models in a BIM environment.

In addition, the on-site surveys allowed us to verify and, if necessary, refine the geolocation of the heritage asset and to record it through an appropriate photographic campaign, accompanied by a documentary section containing historical sources, images, and bibliographical references (Figure 4). Historical data, drawn from both published and unpublished sources, is crucial in this field. Currently, there is insufficient data to establish precise chronological ranges for the construction and use of the mills, so they will not be discussed in this context. However, future activities planned in the M.A.C.IN.A. project aim to collect this information, thereby enhancing our understanding of this lesser-known aspect of historical heritage.

The data has been organized and processed using tables and spreadsheets, made interoperable thanks to the introduction of a unique identification code, “ID Mill,” which has allowed for the integration of different types of data, including links to photographs taken during field activities (Figure 5).

The collected data enabled the classification of buildings according to their historical function, allowing for the identification of grain mills, paper mills, sawmills, copper mills, and hydropower for electricity structures (Figure 6a). Furthermore, the current state of the surveyed structures was assessed, with particular attention to ownership status and intended use. The analysis revealed that many watermills are now under private ownership, while only a limited number remain publicly owned. The private ownership of the buildings affected the collection of data in the field, as it meant that the sites were not always accessible. As a result, it was not possible to determine the functionality of 17% of the mills identified through IGM cartography.

Among the buildings for which current use was identified, some still function as mills—although predominantly powered by electricity—while others have been converted into private residences or accommodation facilities. Some buildings were found to be under renovation, with their final use yet to be defined (Figure 6b).

Another analysis aims to assess the condition of the historic channels—i.e., the water headrace and tailrace—as these are a fundamental element of hydraulic mills. The analysis focused on the recognizability and physical preservation of these canals to identify structures in which the original hydraulic system is still visible (Figure 6c). In several cases, the hydraulic power once required to operate the mills is now compromised or absent due to the interruption of headrace and tailrace or the loss of diversion works. These elements are subject to significant degradation, often attributable to extreme flooding events that lead to damage and ultimately the loss of these structures.

The dataset analysis was developed using QGIS, an open-source software platform that enabled cross-referencing between historical buildings and their surrounding environments. Part of the data used originated from the Technical Regional Map (CTR), which allowed for the digitization of the hydrographic network in the L’Aquila area of Abruzzo, including rivers, canals, and streams, as well as the buildings situated along these waterways. The derived data from CTR analysis was then compared with information extracted from IGM cartography, which had been used to identify the watermills. At this stage, the latter were digitized as point features, each assigned an ID from the previous step, facilitating data linkage for visualization within the GIS environment (Figure 7).

Aware of the partiality of the data, since the absence on this map does not correspond to a real absence in the territory, the watermills were analyzed and interpreted based on the territorial data. Each digitized watermill was systematically analyzed by visually comparing current satellite imagery with the primary cartographic sources available on the geoportal. These sources included OpenStreetMap (OSM), the topographic map, the IGM map, the Technical Regional map (CTR), and the Digital Surface Model (DSM). The latter enabled assessment of the local terrain morphology and facilitated the identification of the distribution of historical headrace and tailrace, which are often still detectable through altimetric or morphological variations.

To further enrich the spatial dataset and verify the conservation status of both the structures and their associated hydraulic infrastructure, orthophotos available through the geoportal were also examined, both at a territorial scale and at the level of individual structures. This analysis revealed elements often undetectable in cartographic sources alone, such as ditch traces, recent alterations, vegetation growth, and site accessibility.

As an illustrative case analysis, we focus on the structure identified as EP 24, a mill located within the municipality of L’Aquila. The integration of satellite imagery, cartographic data, and the DSM enabled the reliable identification of the structure and reconstruction of the canal route connecting it to the primary watercourse. The results reinforce the importance of diversion infrastructure as both a functional element of historic hydraulic systems and a key resource for the interpretation and enhancement of cultural river landscapes (Figure 8).

The analysis of orthophotos also enabled the identification of vegetation changes and morphological variations over time, providing valuable insights into the structural evolution, degree of integrity, and state of conservation of the sites. When compared with cartographic sources and the Digital Surface Model (DSM), this information contributed to reconstructing landscape transformations and interpreting traces of disused hydraulic infrastructure (Figure 9).

4. Watermills and Risks: Data Interpretation and Visualization in a GIS Environment

The visualization and interpretation of data in a GIS environment have enabled the production of a series of thematic maps aimed at classifying and integrating data on hydraulic structures, as well as relating them to the main environmental and territorial factors. The buildings surveyed were classified according to multiple parameters, including their state of conservation, construction type, the presence or absence of historic canals, and their relationship with the current hydrographic network. Particular attention was paid to the relationship between these structures and water, which, as a central element and essential driving force, was once present but is now often absent due to changes in land management.

In this context, the thematic maps developed represent tools for reading and interpreting the territory, capable of illustrating the distribution of hydraulic mills along the Aterno basin and its main tributaries. In the map shown in Figure 10, the watermills are categorized according to their concentration in the territory. There is a noticeable concentration of mills in the upper valley of the Aterno River, particularly in the municipalities of Barete and Pizzoli, as well as in L’Aquila, which are located near both the Aterno and the Vera Rivers. The concentration of watermills in the municipality of Molina Aterno is particularly significant, given that its name reflects this historic characteristic because the place name “Molina” is an etymological derivation of the Latin term that referred to a mill.

The distribution of the mills should be analyzed in relation to the area’s orographic features, which likely influenced the creation of the headrace and tailrace canals.

Additionally, the variation in altitude plays a significant role in creating the potential energy necessary to operate the mills. An examination of the mills marked on the IGM map indicates that there are fewer mills in the flatter regions of the river compared to the mountainous areas.

In Figure 11, the watermills have been classified according to their functional condition and layered onto the protected areas map of the Abruzzo region. This cross-reference relates to the percentage of protected areas, which accounts for 37% of the territory, making it the Italian region with the largest protected area in relation to its total surface area.

Only in specific cases has the location of the mill in a protected area determined its state of maintenance, which, in general, does not appear to be influenced by this aspect.

Figure 12 shows the map for cross-referencing data on the state of headrace and tailrace with the risk of flooding inferred from the PSDA cartography of the Abruzzo Region. In the map, the level of risk is represented on a scale of four values, from R1 (low risk) to R4 (high risk). In total, 10 of the 64 mills surveyed, or 15.6% of the total, are in an area with a high risk of flooding, classified as R4. One other mill is placed in an area with a low risk of flooding, R1. The situation described is to be considered entirely normal, both because mills are often located adjacent to the main watercourse and because mills are commonly positioned to influence the watercourse, which can increase their vulnerability.

Cross-analysis of data in a GIS environment with visualization of risk maps and field-collected data, including photos of past floods, demonstrates the usefulness of the research, as these aspects are reflected in the condition of structures and therefore need to be analyzed at the territorial and building scales. A representative example concerns the past flood events that affected the Cavalli mill, located in the municipality of Pizzoli (EP 13) and still in operation. Specifically, two floods that occurred in recent decades have impacted the area, highlighting not only the structural vulnerability to extreme events but also the need for protection and adaptation strategies that are compatible with the site’s historical memory (Figure 13). Some photos show several people repairing a small dam upstream of the mill, damaged by flooding at the end of the last century. These images provide evidence of the site’s historical memory and the close relationship between flood risk and buildings, as flooding can significantly compromise the state of conservation and structural health of buildings.

In the map shown in Figure 14, the conservation status of the mills is represented in relation to landslide risk and other hydrogeological hazards derived from the PAI. The enlarged inset highlights a representative case of a mill in a ruined state, located in an area classified as hydrogeological risk R1. Although the risk is low-level, it is interesting to note that the paper mill is already classified as a ruin in the IGM cartography. This could be significant and indicate historical instability that led to the structure’s abandonment. More in-depth research is underway to confirm or refute this hypothesis.

The documents described above highlight the risk factors threatening the conservation of the mills: on one hand, the progressive abandonment which has significant consequences on the conservation of the artifacts, and on the other, the natural hazards affecting the entire Apennine territory. From this perspective, the thematic maps are not merely tools for documentation but become operational supports for planning protection and enhancement actions for the river landscape, within a framework of sustainable and participatory development.

5. Conclusions

The survey presented in this paper highlighted the decisive role of two-dimensional graphic representation in a GIS environment for understanding and interpreting the environmental and landscape phenomena involving the watermills located in the Aterno valley, revealing the past and present interaction between the structures and the water canals, historic crossing structure, such as bridges, and ancient road networks.

However, the research also highlighted the current vulnerabilities affecting this heritage: the abandonment of traditional production practices, together with natural risks—in particular extreme hydrogeological risks linked to climate change, and ongoing seismic risks specific to this area—have accelerated the physical deterioration of the buildings and contributed to the loss of the historical memory associated with them. The results of this survey indicate the need for an integrated approach to conservation and enhancement of the surviving artifacts, capable of combining historical knowledge, territorial analysis, and sustainable regeneration strategies.

In this regard, further research aims to integrate the data collected with historical sources preserved in the State Archives of L’Aquila and with the results of field surveys conducted using archeological research methodologies, to broaden knowledge and to place the construction and use of the artifacts within chronological ranges. At the same time, a collaboration with geologists has been established to analyze fluctuations in water availability over time in relation to historical climate oscillations, through a hydrogeological–hydroclimatic approach, which remains relatively unexplored in reconstructions of the evolution of ancient societies. This approach will contribute to a deeper understanding of the built landscape, reconstructing the historical evolution of the artifacts that still exist and, at the same time, understanding the processes that led to the disappearance of numerous watermills that were once integrated into the river production system.