Lost Landscape: a Combination of Lidar and APSFR Data to Locate and Contextualize Archaeological Sites in River Environments

remote sensing

Article Lost Landscape: A Combination of LiDAR and APSFR Data to Locate and Contextualize Archaeological Sites in River Environments

Esther Rodríguez González * , Pablo Paniego Díaz and Sebastián Celestino Pérez

Instituto de Arqueologia (CSIC—Junta de Extremadura), 06800 Mérida, Spain; [email protected] (P.P.D.); [email protected] (S.C.P.) * Correspondence: [email protected]

Abstract: Over the last few decades, river landscapes have been significantly transformed as a result of increased human impact. This transformation is evident in areas such as the middle Guadiana basin, where the impact of both agricultural and hydraulic infrastructures has led to the decontextualization of archaeological sites, resulting in a disconnection between archaeological sites and their own physical environment. In order to analyse the location and geographic contexts of sites from the first Iron Age in the middle Guadiana basin and to detect the existence of human settlement patterns, we designed a methodological approach that combines LiDAR and APSFR data (areas with potential significant flood risk). The main purpose of this method is to detect flood areas and assess the relationship between them and archaeological sites. The result allowed us to obtain a clearer understanding of these societies, their knowledge of the physical environment, and the causes Citation: Rodríguez González, E.; and reasons behind their occupation of certain sites. The validation of the results demonstrated the Paniego Díaz, P.; Celestino Pérez, S. versatility of this methodological approach, which can be extrapolated to analysing other regions Lost Landscape: A Combination of and historical periods. LiDAR and APSFR Data to Locate and Contextualize Archaeological Keywords: Sites in River Environments. Remote LiDAR; potential flood risk; aerial archaeology; landscape archaeology; Tartessos; middle Sens. 2021, 13, 3506. https:// Guadiana basin doi.org/10.3390/rs13173506

Academic Editors: Antonio Monterroso Checa and Dimitrios D. 1. Introduction Alexakis The middle basin of the River Guadiana is an extensive area in the southwest of the Iberian Peninsula (Figure1). It is structured around one of the main rivers of the peninsula, Received: 16 June 2021 the Guadiana, which has a hierarchical network of tributaries that make it a fundamental Accepted: 31 August 2021 artery of communication. The Guadiana is a low-lying river, shallow and easy to ford [1] Published: 3 September 2021 (p. 29), making it an essential element that must be present in any analysis of ancient settlement in this region, given the migratory role the river played. Publisher’s Note: MDPI stays neutral The fertility of the soil along the Guadiana River has favoured the occupation of the with regard to jurisdictional claims in area from prehistoric times to the present day. However, local archaeological remains are published maps and institutional affil- in a poor state of preservation, due to agricultural work carried out in the area, which has iations. led to the transformation of the landscape and the destruction of a large number of sites that are hidden under the current croplands. To overcome this situation, archaeologists use different landscape analysis tools and methodologies and remote sensing to facilitate our work by creating predictive models that give us a better understanding of how the Copyright: © 2021 by the authors. landscape functioned in ancient times. The final aim of this work is to historically interpret Licensee MDPI, Basel, Switzerland. the cartographic data to understand the relationships that ancient societies in the area had This article is an open access article with the landscape in which they lived. distributed under the terms and Given the close relationship between the Guadiana River and the settlement of this conditions of the Creative Commons territory, in order to determine to what impact the river course has had on the settlements, Attribution (CC BY) license (https:// and more specifically settlements from the first Iron Age, we designed an analysis strategy creativecommons.org/licenses/by/ that incorporates data from the calculation of Areas with Potential Significant Flood Risk 4.0/).

Remote Sens. 2021, 13, 3506. https://doi.org/10.3390/rs13173506 https://www.mdpi.com/journal/remotesensing Remote Sens. 2021, 13, 3506 2 of 28

(APSFR) provided by the Guadiana River Hydrographic Confederation (CHG, dependent on the Spanish Ministry for Ecological Transition and Demographic Challenge); the traditional study carried out from the review of current and historical aerial photographs, and the spatial analysis made from the data provided by LiDAR flights. Calculating the flood areas of the Guadiana riverbed and of some of its main tributaries allows us to delimit the area within which the course of the river shifted, hence the importance of this study and of the methodology it contains. With this image, we can determine the position of the sites with respect to the river, their distance or proximity, and estimate to what extent a site is impacted, or the symbolic significance of the places that were chosen to locate a site. Although the working methodology presented in this article can be applied to any chronology, since the main variable of this formula is the location of the sites with respect to the watercourses in each historical moment, we selected the period comprising the first Iron Age in the middle Guadiana basin, between the seventh and fifth centuries BC. At this moment in time, the area was experiencing demographic growth as a result of the crisis that occurred in the heart of Tartessus, the Guadalquivir valley [2], which would Remote Sens. 2021, 13, 3506 result in the appearance of a new model of settlement that was unparalleled in other3 of 29

Mediterranean regions.

FigureFigure 1. Map 1. Map showing showing settlements settlements inin thethe middle middle Guadiana Guadiana basin basin during during the firstthe Ironfirst Age.Iron 1.Age. Huerta 1. Huerta de Don de Mateo; Don 2. Mateo; Casas 2. Casas del Cerro de la Barca; 3. Cañada la Virgen; 4. Miraflores; 5. Lácara; 6. Turuñuelo de Mérida; 7. El Tiriñuelo; 8. Turu- del Cerro de la Barca; 3. Cañada la Virgen; 4. Miraflores; 5. Lácara; 6. Turuñuelo de Mérida; 7. El Tiriñuelo; 8. Turuñuelo ñuelo (Villagonzalo); 9. Las Madalenas; 10. Casas del Turuñuelo: 11. Las Lomas; 12. La Aliseda; 13. La Mata; 14. Cancho (Villagonzalo); 9. Las Madalenas; 10. Casas del Turuñuelo: 11. Las Lomas; 12. La Aliseda; 13. La Mata; 14. Cancho Roano; Roano; 15. El Tamborrio; 16. Escuela de Hostelería (Mérida); 17. El Chaparral; 18. El Palomar; 19. La Marquesa; 20. Mede- 15. El Tamborrio; 16. Escuela de Hostelería (Mérida); 17. El Chaparral; 18. El Palomar; 19. La Marquesa; 20. Medellín; 21. La llín; 21. La Veguilla; 22. Cerro Manzanillo; 23. Cerro de la Barca—Torruco; 24. Media Legua; 25. La Carbonera; 26. La Mata Veguilla; 22. Cerro Manzanillo; 23. Cerro de la Barca—Torruco; 24. Media Legua; 25. La Carbonera; 26. La Mata de Cancho de Cancho Roano; 27. Las Reyertas; 28. Necropolis of Aljucén; 29. Necropolis of El Pozo; 30. Necropolis of Valdelagrulla. Roano; 27. Las Reyertas; 28. Necropolis of Aljucén; 29. Necropolis of El Pozo; 30. Necropolis of Valdelagrulla.

2. TheThe Middle population Guadiana of the Basin: middle An Guadiana Anthropized basin Territory during the ﬁrst Iron Age was charac- terisedIn order by the to presenceunderstand of large the importance structures at of the th conﬂuenceis study, it ofis theimportant Guadiana to consider and some the profound changes that the landscape of the central Guadiana basin has undergone over the last century, and how this process has affected the archaeological record. The transformation of the Vegas del Guadiana experienced a major boost in the 1950s, when the General Economic and Social Development Plan for the Province of Badajoz, known as the Badajoz Plan, began to be implemented [4]. The work plan included the construction of hydraulic infrastructures, the adaptation of the necessary roads in the irrigation area, and the construction of new villages to house workers. The project included the irrigation of more than 120,000 hectares, the construction of 60 villages, and the planning of 8 reservoirs and 4 irrigation canals [5]. This colossal project entailed a radical change in the structure and image of the landscape, which went from being represented by large expanses of unirrigated land to being a green, irrigated landscape with alternating crops of tomato, rice and maize. This change also entailed the replacement of the native vegetation of the territory and the destruction of a large number of enclaves, irretrievable information that has left little trace in the archaeological record (Figure 2).

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of its main tributaries. There is only one exception to this pattern: the sites of Cancho Roano (Zalamea de la Serena, Badajoz, Spain) and La Mata (Campanario, Badajoz, Spain) located inland to the south of the river. All these structures have several characteristics in common, starting with the material used for their construction (adobe) and the way in which they were re-used. After their destruction and abandonment, these buildings were hidden under a large artiﬁcial mound that helped to conserve them until the present day. Along with the so-called Tartessian buildings hidden under tumuli, the settlement model is completed with the presence of settlements on high ground, village and farm-type sites on plains, and the necropolis (Figure1). All of them form a hierarchical settlement model in which the Cancho Roano and Casas del Turuñuelo-type buildings play an important political and economic role [3]. Therefore, in order to demonstrate the effectiveness of the proposed methodological model, we selected several case studies that include examples corresponding to each of the settlement categories presented in the middle Guadiana basin. In the case of the necropolis, we present the results of El Pozo—Medellín, and the nearby settlement of Medellín (Badajoz, Spain); a village- or farm-type settlement represented by Cerro de la Barca—Torruco (Villanueva de la Serena, Badajoz, Spain), and an overview of the results obtained after applying the proposed methodology to the location of the so-called Tartessian buildings hidden under tumuli.

2. The Middle Guadiana Basin: An Anthropized Territory In order to understand the importance of this study, it is important to consider the profound changes that the landscape of the central Guadiana basin has undergone over the last century, and how this process has affected the archaeological record. The transformation of the Vegas del Guadiana experienced a major boost in the 1950s, when the General Economic and Social Development Plan for the Province of Badajoz, known as the Badajoz Plan, began to be implemented [4]. The work plan included the construction of hydraulic infrastructures, the adaptation of the necessary roads in the irrigation area, and the construction of new villages to house workers. The project included the irrigation of more than 120,000 hectares, the construction of 60 villages, and the planning of 8 reservoirs and 4 irrigation canals [5]. This colossal project entailed a radical change in the structure and image of the landscape, which went from being represented by large expanses of unirrigated land to being a green, irrigated landscape with alternating crops of tomato, rice and maize. This change also entailed the replacement of the native vegetation of the territory and the destruction of a large number of enclaves, irretrievable information that has left little trace in the archaeological record (Figure2). In addition to the transformation of the landscape, the construction of the reservoirs that currently regulate the Guadiana River has led to a reduction in its volume, the drying up of many of its tributaries that were operational in ancient times, and the displacement and channelling of others to use their waters for irrigating crops. The impact of this anthropization process is so considerable that in many cases, it is not even possible to locate the paleochannels of the rivers with the aid of current aerial photography, let alone to deﬁne the width of the original course of such important arteries as the Guadiana itself. The vast majority of these branches have been ﬁlled in with soil, and are currently occupied either by buildings or farmland (Figure3). Perhaps the closest example we have to appreciate the impact of the Badajoz Plan on cultural heritage is the Alqueva Dam Construction Plan in the Portuguese Alentejo region, inaugurated in 2002. This project has had an enormous impact on the landscape, the environment, and heritage assets; however, in contrast to the Alqueva Project, its execution included a programme to minimise the impact of the work on heritage assets, making it possible to document and safeguard a large number of settlements that were previously unknown, as well as to reduce the damage that this type of infrastructure causes to these remains [6]. Remote Sens. 2021, 13, 3506 4 of 28 Remote Sens. 2021, 13, 3506 4 of 29

FigureFigure 2.2. AerialAerial photographs photographs of of the the section section of of the the Gu Guadianaadiana between between the the Búrdalo Búrdalo and and Ruecas Ruecas tributaries showing the impact on the landscape caused by the implementation of the Badajoz Plan. (A) tributaries showing the impact on the landscape caused by the implementation of the Badajoz Plan. Photograph from the American flight of 1945/1946. (B) Still from the PNOA Máxima Actualidad. (A) Photograph from the American ﬂight of 1945/1946. (B) Still from the PNOA Máxima Actualidad.

InIn light addition of this, to the maintransformation objective of of this the studylandscape, is to contribute the construction to the reconstructionof the reservoirs andthat comprehension currently regulate of the the ancient Guadiana landscape River has of theled middleto a reduction Guadiana in its basin. volume, Only the in drying this wayup of will many we of be its able tributaries to understand that were how operational this area was in ancient structured times, in and ancient the displacement times, and assessand channelling the areas chosen of others for the to locationuse their of waters the enclaves. for irrigating We will crops. also be The able impact to evaluate of this the an- rolethropization the river played process in is the so life considerable of the societies that thatin many inhabited cases, this it is area. not Whateven possible are the reasons to locate orthe determining paleochannels factors of the that rivers led a groupwith the to selectaid of certaincurrent spaces aerial as phot idealography, sites to let establish alone to theirdefine settlements the width or of necropolises? the original course of such important arteries as the Guadiana itself. The Tovast date, majority in order of these to achieve branches this objectivehave been and filled to approachin with soil, the and conﬁguration are currently of theoccu- landscapepied either during by buildings antiquity, or farmland we resorted (Figure to different 3). disciplines such as carpology and palynology,Perhaps thanks the closest to which example we managed we have to to identify appreciate the plantthe impact species of foundthe Badajoz in this Plan area on duringcultural protohistory heritage is the and Alqueva to reconstruct, Dam Constructi approximately,on Plan in the the palaeoenvironment Portuguese Alentejo of region, this territoryinaugurated during in 2002. speciﬁc This periods project of has history, had an such enormous as the Iron impact Age on [7]. theWe landscape, also undertook the en- costlyvironment, geomorphological and heritage work. assets; In however, regions as in transformed contrast to the as the Alqueva middle Project, basin of its the execution River Guadiana,included a this programme work must to be minimise accompanied the impact by geotectonic of the work analysis on andheritage OLS datingassets, inmaking order it topossible date and to reconstructdocument theand structure safeguard of thea large geological number model of settlements of the environment that were of previously the sites, orunknown, the terraces as thatwell the as riverbedsto reduce havethe damage shaped overthat this the years.type of These infrastructure methods complicate causes to thethese taskremains of analysing [6]. large swathes of territory that may contain a significant number of sites. In this sense,In light for of the this, time the being main in theobjective middle of Guadiana this study basin, is to we contribute only carried to the out reconstruction work in the area of Medellín, aimed at providing an approximate characterisation of its morphogenetics and comprehension of the ancient landscape of the middle Guadiana basin. Only in this through the analysis with GIS tools. More detailed and complete field work is still pending way will we be able to understand how this area was structured in ancient times, and that will make it possible to verify the data collected from the cartography [8,9]. assess the areas chosen for the location of the enclaves. We will also be able to evaluate the role the river played in the life of the societies that inhabited this area. What are the

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Despite the changing and dynamic environment that characterises alluvial landscapes [10], it is not uncommon to use the current state of the landscape as a reference point and insert ancient populations into it, without assessing to what extent this space has been Remote Sens. 2021, 13, 3506 5 of 29 transformed over time. Detailed studies on these morphological changes have revealed how conditions in ancient times were different from those of today, and this is reﬂected in the detection, preservation and interpretation of sites, as well as in the documentation ofreasons ﬂood eventsor determining [11–13]. Unfortunately, factors that led studies a group of this to select kind arecertain still lackingspaces inas theideal middle sites to Guadianaestablish their basin. settlements or necropolises?

FigureFigure 3.3. Comparison between a still from from the the American American Flight Flight of of 1945/1946 1945/1946 (A (A) and) and an an image image cor- correspondingresponding to tothe the PNOA PNOA MáximaMáxima Actualidad Actualidad (B),(B where), where we we can can see see the the impact impact that that the the Badajoz Badajoz Plan caused by cutting off paleochannels that were filled in and are now used as farming areas. The Plan caused by cutting off paleochannels that were ﬁlled in and are now used as farming areas. The images show how two branches of the River Ortigas, a tributary of the Guadiana which flowed next to images show how two branches of the River Ortigas, a tributary of the Guadiana which ﬂowed next the Iron Age necropolis of Valdelagrulla, have been eliminated and are now occupied by orchards. to the Iron Age necropolis of Valdelagrulla, have been eliminated and are now occupied by orchards.

3. MaterialsTo date, and in Methodsorder to achieve this objective and to approach the configuration of the landscape during antiquity, we resorted to different disciplines such as carpology and Traditionally, laboratory studies aimed at obtaining geomorphological data in certain palynology, thanks to which we managed to identify the plant species found in this area geographic areas begin by comparing current aerial photographs, available in the National during protohistory and to reconstruct, approximately, the palaeoenvironment of this ter- Aerial Orthophotography Plan (PNOA), with the photograms obtained from the American ritory during specific periods of history, such as the Iron Age [7]. We also undertook costly Flight, both Series A, taken between 1945 and 1946, and Series B, corresponding to the years geomorphological work. In regions as transformed as the middle basin of the River Gua- 1956–1957. This latest series of photogrammetric ﬂights contain the oldest images available ofdiana, the Iberian this work Peninsula must tobe determineaccompanied the stateby geotectonic and structure analysis of the territory,and OLS indating our speciﬁc in order to date and reconstruct the structure of the geological model of the environment of the sites, or the terraces that the riverbeds have shaped over the years. These methods complicate the task of analysing large swathes of territory that may contain a significant number of sites. In this sense, for the time being in the middle Guadiana basin, we only carried out work in the area of Medellín, aimed at providing an approximate characterisation of its morphogenetics through the analysis with GIS tools. More detailed and complete field

Remote Sens. 2021, 13, 3506 6 of 28

case, prior to the implementation of the Badajoz Plan. As such, these are the images that come closest to the configuration that the territory would have had in ancient times. As a complement to the comparative study between historical and current aerial photograms, we now present a new methodology in which two types of data are combined: LiDAR and the Areas with Potential Significant Flood Risk (APSFR), specifically those regions that are confined to the middle Guadiana river basin. The combination of both sources of information constitutes a new approach to geoarchaeological studies and the reconstruction of the paleo-landscape of a region, by allowing us to explore the configuration that fluvial arteries such as the Guadiana would have had in ancient times. The use of LiDAR technology for the remote sensing of archaeological sites is a regular process in any archaeological project, whether in settlement or landscape studies [14–16]. This is due to the usefulness of the results provided by this tool in providing a precise image of the ground surface. Their level of detail makes it possible to document surface anomalies by algorithmically removing excess information, such as vegetation, which eliminates background noise when interpreting the presence of structures that belong to an archaeological site. The combination of Digital Elevation Models (DEMs) obtained from the processing and filtering of the point cloud acquired in the LiDAR flight with other tools, such as historical photography or filtering programmes that allow the presence of these anomalies in the terrain to be highlighted by shading, has emphasised the suitability of this technology within the field of archaeology. Its use for detecting sites is widely known [17]; however, there are fewer studies that use it for the topographical characterisation of a terrain or for the reconstruction of the ancient landscape [18–24]. In contrast to the usual use of LiDAR, data from the Preliminary Flood Risk Assess- ment (PFRA) have never been applied in western Europe in a study whose main objective is to reconstruct the ancient landscape. Mapping the regions defined as Areas of Potential Significant Flood Risk (APSFR) makes it possible to assess the expected depth in the event of flooding. These data, therefore, reflect the difference between the ground elevation at the time of the simulation and the height that the water would reach in the return periods. In the data provided by the Guadiana River Basin Authority (CHG), three return periods are grouped together: T10, T100 and T500, pointing towards the existence of events that would potentially occur once every 10, 100 or 500 years. Although this information is available for all the rivers of the Iberian Peninsula and in each region, they have a different recording pattern: the first floods documented by the CHG date back to the year 620 CE. Since that date, many events have been recorded, although data were not systematically gathered until 1935. Although we are aware of the current nature of the data and the need to perform geomorphological studies in order to confirm the hypotheses, the use of ARSPI allows us to make a first contact with the ancient topography of the Guadiana and the areas through which the river and its tributaries must have flowed. At this point, it is necessary to highlight the restricted mobility of the Guadiana over the last few millennia due to the topography of the territory. This fact is reinforced by the absence of archaeological sites under alluvial formations, and also by the existence of remains of Roman bridges in Mérida and Medellín [25]. Although the construction of dams has affected the flow of the river and its regulation, the comparison with the photograms of the American Flight reveals the absence of significant changes in its course as a result of these works. In this way, ARSPI allows us, for example, to identify small clogged branches, and the area where the minor variations in their course occurred within a delimited area, possibly restricted to the T10 events. As we can see below, the application of these data and their superimposition on a DTM allows us to accurately approach the palaeogeography of the Guadiana and some of its tributaries, in order to analyse the position that the sites of the first Iron Age occupied in the landscape, and how they may have been affected by flooding. Fortunately, this archaeological work can be carried in Spain at no cost. All the data, both aerial photographs and LiDAR, are available to download from the server of the National Geographic Information Centre (CNIG), which depends on the National Remote Sens. 2021, 13, 3506 7 of 29

Although we are aware of the current nature of the data and the need to perform geomorphological studies in order to confirm the hypotheses, the use of ARSPI allows us to make a first contact with the ancient topography of the Guadiana and the areas through which the river and its tributaries must have flowed. At this point, it is necessary to highlight the restricted mobility of the Guadiana over the last few millennia due to the topography of the territory. This fact is reinforced by the absence of archaeological sites under alluvial formations, and also by the existence of remains of Roman bridges in Mérida and Medellín [25]. Although the construction of dams has affected the flow of the river and its regulation, the comparison with the photograms of the American Flight reveals the absence of significant changes in its course as a result of these works. In this way, ARSPI allows us, for example, to identify small clogged branches, and the area where the minor variations in their course occurred within a delimited area, possibly restricted to the T10 events. As we can see below, the application of these data and their superimposition on a DTM allows us to accurately approach the palaeogeography of the Guadiana and some of its tributaries, in order to analyse the position that the sites of the first Iron Age occupied in the landscape, and how they may have been affected by flooding. Fortunately, this archaeological work can be carried in Spain at no cost. All the data, Remote Sens. 2021, 13, 3506 both aerial photographs and LiDAR, are available to download from the server 7of of 28the National Geographic Information Centre (CNIG), which depends on the National Geo- graphic Institute (IGN) [26], as well as on the website of Spatial Data Infrastructures of ExtremaduraGeographic Institute (IDEEx) (IGN) [27], for [26 ],the as region well as in on wh theich website our study of Spatial area is Data located. Infrastructures Additionally, of theExtremadura Ministry for (IDEEx) Ecological [27], Transition for the region and in Demographic which our study Challenge, area is located.within its Additionally, Spatial Data Infrastructurethe Ministry for (SDI), Ecological makes Transition the APSFR and cartogra Demographicphy available Challenge, to users within [28]. its In Spatial our specific Data caseInfrastructure and for the (SDI), drafting makes of thethis APSFR study, cartographythe APSFR information available to userswas provided [28]. In our directly specific by thecase Guadiana and for the River drafting Basin of Authority this study, (CHG). the APSFR information was provided directly by the GuadianaThe first River step Basin in our Authority methodology (CHG). (Figure 4) corresponds to downloading the data. AlthoughThe firstthe National step in our Geographic methodology Institute (Figure ha4s) two corresponds LiDAR flights, to downloading the first from the 2008 data. to 2015Although and the the second National from Geographic 2015 to the Institute present has day, two we LiDAR selected flights, the data the from first fromthe first 2008 flight to for2015 our and study, the second as the fromsecond 2015 flight to the is presentnot yet day,available we selected for the the entire data peninsula. from the first Although flight thefor IGN our study, has the as LiDAR the second data flight already is not classified, yet available we selected for the entirethe raw peninsula. data in order Although to in- cludethe IGN the hasmechanisms the LiDAR that data we use already in the classified, classification we selectedand transformation the raw data of inthe order data and to theinclude subsequent the mechanisms obtaining that of the we Digital use in theTerrain classification Model (DTM) and transformation in the workflow, of the which data is mappingand the subsequent that serves obtaining as the basis of thefor Digitalthe visualisation Terrain Model of the (DTM) results in of the our workflow, study. which is mapping that serves as the basis for the visualisation of the results of our study.

Figure 4. Workflow scheme. Figure 4. Workflow scheme. The coverage corresponding to the first LiDAR flight has a resolution of 2 m2 of surfaceThe per coverage point orcorresponding 0.5 points/m to2. Thisthe first resolution LiDAR wasflight more has a than resolution enough of to 2 carrym2 of out surfacethe studyper point proposed or 0.5 here,points/m as it2 dealt. This with resolution an extensive was more territory, than butenough for the to detectioncarry out ofthe studycertain proposed archaeological here, as remains, it dealt greater with an precision extensive is required.territory, Thebut downloadedfor the detection raw of data certain are archaeologicalin .LAZ format, remains, which requires greater decompressionprecision is required. and transformation. The downloaded For this raw purpose, data are we in .LAZused theformat, ARCGIS which 10.5 requires program decompression and the LASTool and extension. transformation. The latter For programmethis purpose, was we useddeveloped the ARCGIS by Martin 10.5 Isenburg program for and LiDAR the dataLASTool processing extension. and isThe free latter to download programme [29]. was Of developedthe tools contained by Martin in Isenburg the LASTool for LiDAR extension, data we processing used the Blast2demand is free extension.to download For [29]. its processing we left the default parameters, only modifying the triangulate variable, as our Of the tools contained in the LASTool extension, we used the Blast2dem extension. For its objective was to eliminate excess information, such as buildings or vegetation, in order to processing we left the default parameters, only modifying the triangulate variable, as our only obtain an image of the terrain surface. The final result is a Digital Elevation Model objective was to eliminate excess information, such as buildings or vegetation, in order to (DEM) which was exported in georeferenced .tif format. The spatial data provided by the IGN are distributed in several grids. Specifically, the data required for our study are distributed between MTN50 grids 776, 777, 778, 779, 752, 753, 754, 804 and 805, divided between zones 29 and 30 in an ETRS 89 coordinate system (Figure5). In order to be able to work with a cartographic base that includes the entire territory under analysis, we have to paste the grids together and create a mosaic. To do this, we used another free downloadable tool, Relief Visualization Toolbox (RVT) [30], developed by the Research Centre of the Slovenian Academy of Science and Arts. The final result is a 2 m resolution DTM with hillshade from a single direction (Azimuth 315, Altitude 45). The aim of this analytical shading was to simulate an illumination of the terrain in order to enhance the visualisation of the relief. The reclassified APSFR data were introduced on the base cartography that was created. The data provided by the CHG are in .shp polygon format. A 35% transparency was applied to them so that the topography of the DTM used as a topographic base was visible. By incorporating the APSFR data into the DTM, we generated the definitive model that we could analyse to see how the river flood events affected the different sites, and compared the dispersion of these events with the historical photography in order to detect and define the presence of palaeo-channels that are currently non-existent or imperceptible. By reviewing the resulting models, we detected some alterations in the final results that can be interpreted as distortions. This localised deformation in some of the case studies Remote Sens. 2021, 13, 3506 8 of 29

only obtain an image of the terrain surface. The final result is a Digital Elevation Model (DEM) which was exported in georeferenced .tif format. The spatial data provided by the IGN are distributed in several grids. Specifically, the data required for our study are distributed between MTN50 grids 776, 777, 778, 779, 752, 753, 754, 804 and 805, divided between zones 29 and 30 in an ETRS 89 coordinate system (Figure 5). In order to be able to work with a cartographic base that includes the entire territory under analysis, we have to paste the grids together and create a mosaic. To do this, we used another free downloadable tool, Relief Visualization Toolbox (RVT) [30], developed by the Research Centre of the Slovenian Academy of Science and Arts. The final result is a 2 m resolution DTM with hillshade from a single direction (Azimuth Remote Sens. 2021, 13, 3506 315, Altitude 45). The aim of this analytical shading was to simulate an illumination8 ofof 28 the terrain in order to enhance the visualisation of the relief. The reclassified APSFR data were introduced on the base cartography that was created.is due The to data the fact provided that the by CHG, the whenCHG calculatingare in .shp the polygon APSFR format. data and A assessing 35% transparency the extent ofwas appliedeach of to the them events, so that takes the the topography current topography of the DTM as a reference.used as a topographic Contemporary base geographical was visible. Byfeatures, incorporating many ofthe them APSFR caused data by into agricultural the DTM, activities, we generated can be detected,the definitive which model distort that the we couldresult analyse of the study,to see ashow they the would river notflood have events existed affected in the the past. different For this sites, reason, and and compared with the the dispersionaim of obtaining of these a events vision aswith close the as historical possible tophotography the orography in oforder the terrainto detect during and thedefine ﬁrst the presencemillennium of palaeo-channels BC, we drew up that a protocolare currently for correcting non-existent these or distortions. imperceptible.

FigureFigure 5. 5.MosaicMosaic of of grids grids that containcontain our our study study territory. territory. In order In orde to haver to ahave basic a cartography basic cartography that covers that the covers entire territorythe entire territoryunder under analysis, analysis, we have we to have paste to each paste one each of the one grids of the together. grids together.

ByThe reviewing first cause the of resulting distortion models, are the plots we ofdetected land used some for alterations growing maize in the at thefinal time results of thatthe can LiDAR be interpreted flight. Given as the distortions. density of This this crop, localised it is impossible deformation to eliminate in some thisof the vegetation case stud- ieslayer is due in theto the process fact ofthat reclassifying the CHG, thewhen LiDAR calculating data, because the APSFR given data its compactness, and assessing the the extenttool identifiesof each of it asthe a solidevents, surface, takes whichthe curre takesnt thetopography height of the as maizea reference. at that Contemporary moment as a geographicalreference. As features, this is sometimes many of up them to two caused metres by high, agricultural this distortion activities, stops thecan floodbe detected, event whichin its distort tracks, representedthe result of in the the study, cartography as they with would a square not have (Figure existed6). in the past. For this The second reason for distortion is due to the tumuli under which the Tartessian reason, and with the aim of obtaining a vision as close as possible to the orography of the buildings are hidden. As we noted in the introduction to this work, one of the characteristics terrain during the first millennium BC, we drew up a protocol for correcting these distortions. of these buildings is the way in which they were buried and hidden under a mound of earth which, like the corn, slows the spread of flooding events by having a level that is sometimes 5 or 6 metres above ground level (Figure7). To see how the flood events directly affect the buildings, the mound must be eliminated, making this space’s height equal to the height of the surrounding territory. In order to eliminate both the vegetation of the plots sown with maize and the tumulus cover, we interpolated the values of the adjoining areas. The final result is a DTM in which the raster cells corresponding to the spaces occupied by the distortions in the base cartography have been reclassified with similar height values to those surrounding them, minimising the impact of the distortion. Remote Sens. 2021, 13, 3506 9 of 29

The first cause of distortion are the plots of land used for growing maize at the time of the LiDAR flight. Given the density of this crop, it is impossible to eliminate this vegetation layer in the process of reclassifying the LiDAR data, because given its compactness, Remote Sens. 2021, 13, 3506 the tool identifies it as a solid surface, which takes the height of the maize at that moment9 of 28 as a reference. As this is sometimes up to two metres high, this distortion stops the flood event in its tracks, represented in the cartography with a square (Figure 6).

Remote Sens. 2021, 13, 3506 10 of 29

the site. However, and given that this would require the excavation of all the sites under Figurestudy,Figure 6. 6.which APSFRAPSFR is analysisanalysisquite complicated, correspondingcorresponding the toto best thethe territory territooptionry is wherewhere to take thethe the TuruñueloTuruñuel contouro tumulus tumulus of the isdistortionsis located located (Mérida, Badajoz, Spain). When observing the area affected by the T500 flood event, some infor- (Mwithérida, a Badajoz,differential Spain). GPS When in the observing field, therefining area affected the area by the of T500 affection flood event, and somereclassification information as mation gaps can be detected (marked with a black rectangle), with a rectangular pattern, which are gaps can be detected (marked with a black rectangle), with a rectangular pattern, which are identified muchidentified as withpossible. the plots Finally, planted and with in maize. order The to densobtainity of the this final crop model,means that both during the DTMthe data and inter- the with the plots planted with maize. The density of this crop means that during the data interpolation APSFRpolation exercisedata are for reclassified the elimination so ofthat vegetation, the flood the data programme present interprets their correct it as a solid extension, surface. thereby exerciseexcluding for themodern-day elimination obstacles of vegetation, (Figure the programme 8). interprets it as a solid surface. The second reason for distortion is due to the tumuli under which the Tartessian buildings are hidden. As we noted in the introduction to this work, one of the characteristics of these buildings is the way in which they were buried and hidden under a mound of earth which, like the corn, slows the spread of flooding events by having a level that is sometimes 5 or 6 metres above ground level (Figure 7). To see how the flood events directly affect the buildings, the mound must be eliminated, making this space’s height equal to the height of the surrounding territory. In order to eliminate both the vegetation of the plots sown with maize and the tumulus cover, we interpolated the values of the adjoining areas. The final result is a DTM in which the raster cells corresponding to the spaces occupied by the distortions in the base cartography have been reclassified with similar height values to those surrounding them, minimising the impact of the distortion. Although this method allows us to eliminate the distortion generated by these topographic anomalies, which were absent in ancient times, the reprocessing of the DTM im- plies a loss of quality and accuracy in the final model. Therefore, we recommend that in the event of having to reclassify parts of the terrain to eliminate the distortions, these should be restricted as much as possible, only covering the areas affected by the distortions, in order to prevent the models from losing visualisation quality. To do this, it would be best to have the real elevation level of the site under study, i.e., its ground level, so that the APSFR analysis would approximate the real orography of the terrain, which would FigureFigureavoid 7.having7. APSFRAPSFR to analysis analysismake an correspondingcorresponding interpolation. toto the Thethe territory territorymodifications where where the theto Casas theCasas model del del Turuñuelo Turuñuelo would burialbe burial re- moundmoundstricted isis to locatedlocated reclassifying (Guareña,(Guareña, it using Badajoz, Badajoz, the Spain). valueSpain). of AlthoughAlthou the realgh the elevationthe entire entire area thatarea tothe to the basethe west west of of the of the sitethe burial hadburial mound, including the site, is affected by the T500 flood event, the elevation of the burial mound mound,when it including was in use the in site, ancient is affected times, by only the havi T500ng flood to remove event, the the elevation artificial of tumulus the burial that mound seals under which the Tartessian building is hidden means that this part of the terrain is not affected. under which the Tartessian building is hidden means that this part of the terrain is not affected.

AlthoughThe resolution this method and correction allows usof tothese eliminate distortions the distortion is fundamental generated in a byproject these of to- this pographickind, as it anomalies,allows us to which prove were the existence absent in of ancient situations times, in thewhich reprocessing the flood events of the DTMdirectly impliesaffected a the loss settlement, of quality causing and accuracy it to be in partly the ﬁnal or completely model. Therefore, flooded. we As recommend we can see below, that inin thethe event case of havingthe middle to reclassify Guadiana parts basin of the during terrain the to first eliminate Iron Age, the distortions,the observation these of events affecting the development of the sites has been fundamental in order to historically interpret them.

Remote Sens. 2021, 13, 3506 10 of 28

should be restricted as much as possible, only covering the areas affected by the distortions, in order to prevent the models from losing visualisation quality. To do this, it would be best to have the real elevation level of the site under study, i.e., its ground level, so that the APSFR analysis would approximate the real orography of the terrain, which would avoid having to make an interpolation. The modifications to the model would be restricted to reclassifying it using the value of the real elevation that the base of the site had when it was in use in ancient times, only having to remove the artificial tumulus that seals the site. However, and given that this would require the excavation of all the sites under study, which is quite complicated, the best option is to take the contour of the distortions with a differential GPS in the field, refining the area of affection and reclassification as much as possible. Finally, and in order to obtain the final model, both the DTM and the APSFR data Remote Sens. 2021, 13, 3506 are reclassified so that the flood data present their correct extension, thereby excluding11 of 29

modern-day obstacles (Figure8).

FigureFigure 8.8. APSFRAPSFR analysisanalysis correspondingcorresponding toto thethe territoryterritory wherewhere thethe TuruñueloTuruñuelo tumulus tumulus isis located located (Villagonzalo, Badajoz, Spain). (A) Calculation of APSFR zones prior to the reclassification of the (Villagonzalo, Badajoz, Spain). (A) Calculation of APSFR zones prior to the reclassification of the land. (B) Representation of the territory affected by the APSFR zones after reclassification of the land. (B) Representation of the territory affected by the APSFR zones after reclassification of the terrain and correction of the distortions. terrain and correction of the distortions. Finally, it should be noted that there is a geographical feature, caused by anthropic The resolution and correction of these distortions is fundamental in a project of this action, which generates a distortion in the models, but which we do not believe needs kind, as it allows us to prove the existence of situations in which the flood events directly correction: the artificial terraces created during the re-division of the territory, which led to the existence of different levels within the same space or region. These anomalies in the orography of the terrain are detected by the presence of straight cuts in the models that stop the extension of the events in their tracks. Of the ten cases analysed in our study, this event is detected in only one of them, which we consider better not to correct for a very simple reason: we do not know which of the two elevations, the lower or the upper one of the terrace, was the original elevation (Figure 9).

Remote Sens. 2021, 13, 3506 11 of 28

affected the settlement, causing it to be partly or completely flooded. As we can see below, in the case of the middle Guadiana basin during the first Iron Age, the observation of events affecting the development of the sites has been fundamental in order to historically interpret them. Finally, it should be noted that there is a geographical feature, caused by anthropic action, which generates a distortion in the models, but which we do not believe needs correction: the artificial terraces created during the re-division of the territory, which led to the existence of different levels within the same space or region. These anomalies in the orography of the terrain are detected by the presence of straight cuts in the models that stop the extension of the events in their tracks. Of the ten cases analysed in our study, this event is detected in only one of them, which we consider better not to correct for a very Remote Sens. 2021, 13, 3506 simple reason: we do not know which of the two elevations, the lower or the upper12 one of of29

the terrace, was the original elevation (Figure9).

FigureFigure 9.9.APSFR APSFR analysisanalysis correspondingcorresponding toto thethe areaarea wherewhere the the La La Aliseda Aliseda tumulus tumulus is is located located (Don (Don Benito, Badajoz, Spain). It shows how both the T100 event and the T500 event stop just on the west Benito, Badajoz, Spain). It shows how both the T100 event and the T500 event stop just on the west and south faces of the mound, creating a straight distortion that marks the boundary of the plot. and south faces of the mound, creating a straight distortion that marks the boundary of the plot. Therefore, the plot on which the settlement is located is at a higher elevation so that the flood event Therefore,has its limits the at plot the on contour which of the the settlement plot. is located is at a higher elevation so that the flood event has its limits at the contour of the plot. 4.4. ResultsResults TheThe overalloverall interpretationinterpretation ofof thethe resultsresults allowsallowsa a homogeneous homogeneousinterpretation interpretation totobe be drawndrawn fromfrom thethe study,study, defining defining the the clear clear relationship relationship between between the the Guadiana Guadiana settlements settlements andand thethe different watercourses (Table (Table 11).). In In order order to to present present the the results results obtained obtained after after the theintegration integration of APSFR of APSFR data data and andreconstruction reconstruction of the of paleo-landscape the paleo-landscape of the of middle the middle Gua- Guadianadiana basin, basin, we weselected selected several several examples examples in in order order to to analyse analyse the the usefulness ofof thethe tooltool dependingdepending on on thethe categorycategory of of settlement settlement to to which which it it is is applied. applied.Given Giventhe theheterogeneity heterogeneity of of thethe locationslocations ofof thethe necropolises,necropolises, wewe selectedselected thethe necropolisnecropolis ofof ElEl Pozo,Pozo, sincesince itit isis thethe best-best- knownknown sitesite ofof itsits kind,kind, andand thethe interpretationinterpretation derivedderived fromfrom itsits studystudy isis highlyhighly significant.significant. ForFor thethe analysisanalysis ofof thethe village-typevillage-type settlements,settlements, wewe selectedselected thethe enclaveenclave ofof CerroCerro dede lala Barca—Torruco,Barca—Torruco, forfor oneone mainmain reason: it is is the the only only enclave enclave known known to to date date to to be be located located in inthe the vicinity vicinity of ofthe the Guadiana Guadiana River, River, since, since, as ascan can be beseen seen in Figure in Figure 1 of1 ofthis this paper, paper, the the rest of the examples are located far inland. Finally, the Tartessian buildings hidden under tumuli were analysed as a whole, given that their location in the landscape is one of the characteristics shared by these constructions, which allows us to obtain an overall assessment of the case studies.

Remote Sens. 2021, 13, 3506 12 of 28

rest of the examples are located far inland. Finally, the Tartessian buildings hidden under tumuli were analysed as a whole, given that their location in the landscape is one of the characteristics shared by these constructions, which allows us to obtain an overall assessment of the case studies.

Table 1. List of sites analysed with respect to the nearest watercourse, their height and the ﬂood events that affect them.

Archaeological Site Settlement Category River Distance River Height Difference Affection Event Necropolis of El Pozo Necropolis c. 160 m c. 6 m T100 Medellín Flat settlement c. 360 m c. 6 m - Cerro de la Barca Flat settlement c. 130 m c. 28 m - Huerta de Don Mateo Tumuli c. 365 m c. 4 m - Casas del Cerro de la Barca Tumuli c. 180 m c. 8 m - Cañada de la Virgen Tumuli c. 705 m c. 4 m T100/T500 Turuñuelo (Villagonzalo) Tumuli c. 125 m c. 3 m T500 Casas del Turuñuelo Tumuli c. 775 m c. 4 m T500 Turuñuelo (Mérida) Tumuli c. 1200 c. 8 m - La Aliseda Tumuli c. 1030 m c. 8 T500

4.1. The Necropolis of El Pozo and the Settlement of Medellín (Badajoz, Spain) The necropolis of El Pozo is located in the municipality of Medellín, in the province of Badajoz, on the left bank of the Guadiana, some 500 m to the west of the elevation where it has traditionally been assumed that the settlement was located at the same time as the necropolis (Figure 10). It was discovered in 1969, and to date, a total of ﬁve archaeological excavations have been carried out, which have documented a necropolis with three phases Remote Sens. 2021, 13, 3506 of occupation between the seventh and ﬁfth centuries BC, and in which14 of 29 three types of

burial have been identiﬁed: in urns, in a pit, in busta, or a combination of both types. [31].

Figure 10. 10. LocationLocation of of the the Cerro Cerro del del Castillo Castillo and and the the Necr Necropolisopolis of of El El Pozo Pozo (Medellín, (Medellí n,Badajoz, Badajoz, Spain). Spain).

To complete the study of the palaeolandscape of the El Pozo necropolis, we analysed its fluvial environment using APSFR data. The mapping generated shows that the space occupied by the necropolis would have been submerged in events T10 and T100. In the T10 events, the only variation detected is that the distance between the riverbed and the necropolis is reduced, while in the T100 events, the necropolis would be completely surrounded by water, suggesting that the necropolis, while in use, may have always been surrounded by water; nevertheless, this is difficult to prove. In contrast, only event T500 would have affected the tombs, submerging the remains under the waters of the Guadiana, because although the necropolis stands on a slight elevation, its level would not be high enough to protect it from flooding (Figure 12). These floods, which occurred every 500 years, have been fossilised in the archaeological record. In the stratigraphic sequence of the necropolis, there are traces of some events. Specifi- cally, Stratum II, 0.25 m thick, has been related to the flooding of the river between 1940 and 1941, while Stratum III, which is thicker, reaching up to 2 metres in some points and covering the entire area of the necropolis, would be the result of various periods of flooding [33]. Today, this process still occurs, with the last event documented in the 2013 floods. The process documented in the necropolis of El Pozo is not an isolated event, but is repeated in other case studies documented in the middle Guadiana around its Iron Age necropolises. This is the case for sites such as the necropolis of Valdelagrulla (Medellín, Badajoz, Spain) or Aljucén (Mérida, Badajoz, Spain), where the application of APSFR data corroborated the existence of watercourses that surrounded these funerary spaces in ancient times.

Remote Sens. 2021, 13, 3506 13 of 28

The combination of historical photography, LiDAR data, and APSFR has led to the reveal of results in this particular case study, making it possible to corroborate a hypothesis proposed years ago by the researchers in charge of the excavation of this burial site. Proof of this is a statement from the topographical study carried out in the 1980s, which notes that it occupies a strip of land forming a small elevation above the surrounding area, imperceptible to the naked eye, as it barely stands out 1 metre above the surrounding area. This area, approximately 1 ha in size, must have been located in antiquity between two branches that ran southwards from the current course of the Guadiana, located some 200 m to the north [...]. Both channels are nowadays enclosed and barely visible, as they only resurface during major floods, such as those that occurred in 1969 and 1979, which made it possible to confirm the quasi-island character of the land occupied by the necropolis, an area which, in antiquity, must have been within the riverbed flooded by the usual floods of the Guadiana river.” [32] (p. 894). However, the combination of LiDAR and APSFR data, in this case accompanied by geological mapping and historical photography, allowed us to verify the previous hypothesis and to observe that the floods of the Guadiana caused the area occupied by the necropolis to become a small island. This can be corroborated both by consulting the geological map of the Geological and Mining Institute of Spain (2008), which shows the presence of two branches of the Guadiana that run to the south of the necropolis, currently dried up, and by consulting Series A of the American Flight, where the presence of this small island can be identified, covering an area of 12-13 hectares (Figure 11). To complete the study of the palaeolandscape of the El Pozo necropolis, we analysed its fluvial environment using APSFR data. The mapping generated shows that the space occupied by the necropolis would have been submerged in events T10 and T100. In the T10 events, the only variation detected is that the distance between the riverbed and the necropolis is reduced, while in the T100 events, the necropolis would be completely surrounded by water, suggesting that the necropolis, while in use, may have always been surrounded by water; nevertheless, this is difficult to prove. In contrast, only event T500 would have affected the tombs, submerging the remains under the waters of the Guadiana, because although the necropolis stands on a slight elevation, its level would not be high enough to protect it from flooding (Figure 12). These floods, which occurred every 500 years, have been fossilised in the archaeological record. In the stratigraphic sequence of the necropolis, there are traces of some events. Specifically, Stratum II, 0.25 m thick, has been related to the flooding of the river between 1940 and 1941, while Stratum III, which is thicker, reaching up to 2 metres in some points and covering the entire area of the necropolis, would be the result of various periods of flooding [33]. Today, this process still occurs, with the last event documented in the 2013 floods. The process documented in the necropolis of El Pozo is not an isolated event, but is repeated in other case studies documented in the middle Guadiana around its Iron Age necropolises. This is the case for sites such as the necropolis of Valdelagrulla (Medellín, Badajoz, Spain) or Aljucén (Mérida, Badajoz, Spain), where the application of APSFR data corroborated the existence of watercourses that surrounded these funerary spaces in ancient times. Before concluding the presentation of the results of the study of the palaeolandscape of the necropolis of El Pozo, we would like to highlight an aspect revealed by an analysis of the topography of its surroundings, in relation to a decades-long debate on the location of the settlement associated with this necropolis. Traditionally, an area of scientific research defended the presence of a protohistoric settlement in Medellín, contemporary to the necropolis, which would have been located on the nearest elevation, the hill of Medellín Castle [34]. A review of the 21 interventions carried out on this elevation revealed that there are no occupation levels that allow us to confirm that this elevation was inhabited during the first Iron Age [3], leading us to consider that it was occupied in the Chalcolithic period [35] and Roman period [36]. Remote Sens. 2021, 13, 3506 14 of 28 Remote Sens. 2021, 13, 3506 15 of 29

FigureFigure 11. 11.( A(A)) National National geological geological map map (IGME, (IGME, sheet sheet 778) 778) showing showing the the location location of the of the necropolis necropolis of of ElEl Pozo. Pozo. It It shows shows the the presence presence of of a brancha branch of of the the Guadiana Guadiana running running to theto the south south of theof the necropolis, necropolis, which no longer exists. (B) Photograph of American Flight A (1945/1946) showing the location of which no longer exists. (B) Photograph of American Flight A (1945/1946) showing the location of the the necropolis of El Pozo. The white arrows show the traces of the paleochannels of the Guadiana, necropolis of El Pozo. The white arrows show the traces of the paleochannels of the Guadiana, which which have now dried up. have now dried up.

InBefore contrast concluding to this proposal, the presentation previous studies of the results have alluded of the tostudy evidence of the that palaeolandscape locates the protohistoricof the necropolis settlement of El Pozo, of Medell we wouldín beneath like theto highlight current town, an aspect at the revealed foot of the by southern an analysis slopeof the of topography the hill [2,3 of] (p. its 106)surroundings, (Figure 13 ).in Thisrelati hypothesison to a decades-long gains strength debate after on applying the location ourof the spatial settlement analysis associated methodology with combining this necropolis. LiDAR Traditionally, and APSFR data. an area Interestingly, of scientific the re- proposedsearch defended location the of the presence settlement of a is protohistoric the only point settlement that is safe in from Medellín, flood events.contemporary At the to samethe necropolis, time as the which settlement would was have protected been located from the on floods, the nearest it took elevation, advantage the of hill the of fertile Medel- landslín Castle of the [34]. river A plain. review Thanks of the to21 the interventions insight provided carried by out this on working this elevation methodology, revealed we that canthere now are reaffirm no occupation our hypothesis levels that about allow the locationus to confirm that the that settlement this elevation of Medell wasín inhabited must haveduring occupied the first during Iron Age the first[3], leading Iron Age, us while to consider waiting that for theit was archaeological occupied in studies the Chalcolithic of the projectsperiod [35] carried and out Roman in the period area to [36]. confirm it. In contrast to this proposal, previous studies have alluded to evidence that locates the protohistoric settlement of Medellín beneath the current town, at the foot of the southern slope of the hill [2,3] (p. 106) (Figure 13). This hypothesis gains strength after applying our spatial analysis methodology combining LiDAR and APSFR data. Interestingly, the proposed location of the settlement is the only point that is safe from flood events. At the same time as the settlement was protected from the floods, it took advantage of the fertile

Remote Sens. 2021, 13, 3506 16 of 29

lands of the river plain. Thanks to the insight provided by this working methodology, we

Remote Sens. 2021, 13, 3506 can now reaffirm our hypothesis about the location that the settlement of Medellín15 of 28 must havelands occupiedof the river during plain. Thanksthe first to Iron the insighAge, whilet provided waiting by this for workingthe archaeological methodology, studies we of thecan projectsnow reaffirm carried our out hypothesis in the area about to confirm the loca tionit. that the settlement of Medellín must have occupied during the first Iron Age, while waiting for the archaeological studies of the projects carried out in the area to confirm it.

FigureFigure 12. 12.APSFR APSFR analysis analysis corresponding corresponding to to the the territory territory where where the the necropolis necropolis of El of Pozo El Pozo (Medell (Medellín,ín, Figure 12. APSFR analysis corresponding to the territory where the necropolis of El Pozo (Medellín, Badajoz)Badajoz) is is located. located. It It shows shows how how the the necropolis necropolis was was affected affected by eventby event T500. T500. Badajoz) is located. It shows how the necropolis was affected by event T500.

Figure 13. Cartography showing the hypothetical location of the first Iron Age settlement of Medel- FigureFigure 13. 13.Cartography Cartography showing showing the the hypothetical hypothetical location location of the of ﬁrst theIron first Age Iron settlement Age settlement of Medell of íMedel-n, lín, marked with a black rectangle (Badajoz, Spain). markedlín, marked with with a black a black rectangle rectangle (Badajoz, (Badajoz, Spain). Spain).

Remote Sens. 2021, 13, 3506 16 of 28

4.2. The Village Type Settlement of Cerro de la Barca—Torruco (Villanueva de la Serena, Badajoz, Spain) The site of Cerro de la Barca—Torruco is located in the municipality of Villanueva de la Serena, on a low hill overlooking the Guadiana River, on its right bank [37]. Its location in the landscape, given that it is a small village on a plain, differs markedly from the previous case study, so that the results present us with a very different situation. Despite the fact that this site has never been excavated, its occupation is well defined and delimited both by the presence of abundant archaeological material, which allows for its functional and chronological characterisation, and by the presence of documented remains of structures on the current surface. As far as the dimensions of the enclave are concerned, the survey work allowed us to define a settlement with an approximate surface area of 3 hectares [3] (p. 137). The chronology of the was also determined thanks to the discovery of a bronze plaque with zoomorphic decoration, whose closest parallels have been documented at the site of Cancho Roano (Zalamea de la Serena, Badajoz, Spain). This piece and the presence of type CR-1B amphorae allow us to date the site to between the sixth and fifth centuries BC. The distance between the Cerro de la Barca—Torruco site and the Guadiana River is very close, as the site is currently located 130 m from the riverbank. This led us to consider the possible effect that the river floods could have on the site. The combination of LiDAR and APSFR data allowed us to verify that none of the documented flood events would have affected the site, as it is located at a high enough point to protect it from these events. We can see how the layout of the riverbank at this point has not changed over the years, with the northern end, i.e., the fields or plots located beyond the opposite bank, usually being affected by the increased flow of the river, given that it is in this area where the river’s flood plain is located. The photograph of American Flight B (1956–1957) reveals the presence of several branches of the Guadiana located to the north of the site, which are currently dried out (Figure 14). The presence of both watercourses means that the space between them falls within the area affected by events T10, T100 and T500 (Figure 15). In the past, the regular flooding of the land to the north of the site meant control over fertile stretches of plain that would have favoured the development of agriculture. The position occupied by the enclave, on the slope of the hill overlooking the river, would have allowed it to control both the fertile lands in front of it and the course of the river, whose role as a fundamental artery for the connection between the different enclaves located in the surroundings of its course within the middle section of the River Guadiana is becoming increasingly clearer.

4.3. Tartessian Buildings Hidden under Tumuli in the Middle Guadiana Basin At present, the archaeological work carried out in the middle basin of the Guadiana allowed us to discover a total of 13 tumuli [3] (p. 164). Only three of them have been excavated to date; however, all the information recovered from these interventions provided us with extensive knowledge of the architectural and physical characteristics of these buildings. Cancho Roano (Zalamea de la Serena, Badajoz, Spain) [38] and La Mata (Campanario, Badajoz, Spain) [39] have already been fully excavated, while the structure of Casas del Turuñuelo (Guareña, Badajoz, Spain) [40] is currently in the process of being excavated and studied. As we noted in the introduction to this paper, what we refer to as Tartessian buildings hidden under tumuli are a characteristic system of settlements exclusive to this region during the Iron Age. Their closest parallels are to be found in the Guadalquivir valley, the heartland of Tartessus. They share architectural and material characteristics with these buildings, although the particular feature that makes the Guadiana buildings different from their neighbours in the area of the Guadalquivir is their spatial distribution and the system of destruction and abandonment they suffered at the end of the fifth century BC. The buildings of the middle Guadiana basin were intentionally sealed, destroyed, set on fire, and then covered with earth to effectively conceal them under an artificial mound that protected them from the passage of time. This method of concealment helped to Remote Sens. 2021, 13, 3506 17 of 28

Remote Sens. 2021, 13, 3506 18 of 29 preserve both the constructive remains and the materials, allowing us to discover aspects of Tartessian culture that were hitherto unknown.

FigureFigure 14. 14.Comparison Comparison between between the the orthophotographs orthophotographs of theof Americanthe American Flight Flight B, made B, made between between 1956/19571956/1957 ( A(A) and) and the the PNOA PNOA M áMáximaxima Actualidad Actualidad (B) ( ofB) the of territorythe territory that extendsthat extends to the to north the north of the of the villagevillage of of Cerro Cerro de de la Barcala Barca (Villanueva (Villanueva de la de Serena, la Serena, Badajoz, Badajoz, Spain). Spain). It shows It shows how some how branches some branches of of the Guadiana have dried out. the Guadiana have dried out.

Remote Sens. 2021, 13, 3506 18 of 28 Remote Sens. 2021, 13, 3506 19 of 29

FigureFigure 15.15. APSFRAPSFR analysisanalysis correspondingcorresponding toto thethe territoryterritory inin whichwhich thethe settlementsettlement ofof CerroCerro dedela la Barca—Torruco (Villanueva de la Serena, Badajoz, Spain) is located. It shows that none of the rec- Barca—Torruco (Villanueva de la Serena, Badajoz, Spain) is located. It shows that none of the recorded orded events affect the site. events affect the site.

4.3. TartessianThe proximity Buildings of these Hidden constructions Under tumuli to the in Guadianathe Middle River Guadiana is one Basin of the characteristics sharedAt by present, the Tartessian the archaeological buildings work of the carrie Guadiana.d out in All the except middle four basin are of located the Guadiana at the confluenceallowed us ofto thediscover river witha total one of 13 of tumuli its main [3 tributaries] (p. 164). Only (Figure three 16 ).of Thisthem position have been gave ex- thecavated buildings to date; a strategic however, position all the information that allowed recovered them to dominatefrom these extensive interventions areas provided of land, includingus with extensive fertile plains knowledge for the development of the architec of agriculture;tural and physical at the same characteristics time, they controlled of these onebuildings. of the mainCancho means Roano of communication(Zalamea de la Serena in this, territory:Badajoz, Spain) the rivers. [38] Inand previous La Mata works, (Cam- wepanario, defended Badajoz, the importance Spain) [39] of have the Guadianaalready been as thefully backbone excavated, of the while territory the structure on which of theCasas main del trade Turuñuelo of this (Guareña, region would Badajoz, have Spain) been based[40] is [ 2currently] (p. 256). in Thisthe process hypothesis of being has beenexcavated supported and studied. by the appearance of the first images of boats found at the site of Casas del TuruñueloAs we noted [41 ],in as the well introduction as in the analysisto this paper, of the what amphorae we refer documented to as Tartessian in each build- of theings excavated hidden under sites. tumuli The analysis are a characteristic of the clays sy madestem itof possiblesettlements to verify exclusive the to existence this region of small-scaleduring the commerceIron Age. Their that connectedclosest parallels these sitesare to along be found the Guadiana in the Guadalquivir [42]. valley, the heartlandThe prominent of Tartessus. role theseThey buildingsshare architectural played in theand political material and characteristics territorial organisation with these ofbuildings, this area wasalthough not only the due particular to their locationfeature that in the makes landscape, the Guadiana but also to buildings their architectural different andfrom material their neighbours wealth. Alongside in the area the of the monumental Guadalquivir architecture, is their spatial there distribution are also groups and the of Mediterraneansystem of destruction imports and that abandonment emphasise the they important suffered politicalat the end role of the that fifth these century enclaves BC. playedThe buildings in this area of the between middle the Guadiana sixth and basin fifth we centuriesre intentionally BC [3]. sealed, destroyed, set on fire, Ofand the then total covered number with of documentedearth to effectiv tombely elevationsconceal them in theunder Middle an artificial Guadiana, mound we managedthat protected to examine them from a total the of passage nine using of time. the APSFR This method methodology of concealment proposed helped in this paper:to pre- Canchoserve both Roano, the constructive La Mata, Las remains Lomas and Ltheácara, mate asrials, they allowing are four us enclaves to discover located aspects in the of interiorTartessian of theculture Guadiana, that were next hitherto to one unknown. of its tributaries, but far from the main artery of the Guadiana.The proximity As we of dothese not constructions have predictive to the models Guadiana to evaluate River is theone areasof the with characteris- poten- tialtics floodshared risk by inthe the Tartessian cases corresponding buildings of th toe theGuadiana. tributaries All ofexcept the Guadiana,four are located we do at not the haveconfluence sufficient of the information river with toone evaluate of its main the spatialtributaries relationship (Figure 16). between This position them and gave their the nearby watercourses. buildings a strategic position that allowed them to dominate extensive areas of land, including fertile plains for the development of agriculture; at the same time, they controlled one of the main means of communication in this territory: the rivers. In previous works, we defended the importance of the Guadiana as the backbone of the territory on which

Remote Sens. 2021, 13, 3506 20 of 29

the main trade of this region would have been based [2] (p. 256). This hypothesis has been supported by the appearance of the first images of boats found at the site of Casas del Remote Sens. 2021, 13, 3506 Turuñuelo [41], as well as in the analysis of the amphorae documented in each of 19the of ex- 28 cavated sites. The analysis of the clays made it possible to verify the existence of small- scale commerce that connected these sites along the Guadiana [42].

FigureFigure 16.16. Maps ( A,,B) showing showing the the location location of of the the Tartessian Tartessian buildings buildings hidden hidden under under tumuli tumuli in inre- lation to watercourses. The layout of these constructions always places them next to a watercourse, relation to watercourses. The layout of these constructions always places them next to a watercourse, mainly along the Guadiana, the main communication artery of this territory. mainly along the Guadiana, the main communication artery of this territory.

TheThe applicationprominent role of the these APSFR buildings data played to the DTMsin the political generated and after territorial the processing organisation of theof this LiDAR area flights was not allowed only due us to maketheir location some very in the interesting landscape, observations. but also to their First architec- of all, it shouldtural and be notedmaterial that wealth. all the Alongside elevations the are monu safe frommental the architecture, events that occurthere everyare also 10 groups years. Thisof Mediterranean is quite logical, imports because that if we emphasise take into the account important that the political approximate role that lifespan these ofenclaves these buildingsplayed in isthis about area 100 between years the on average,sixth and preventing fifth centuries the floodsBC [3]. that occur every 10 years from affectingOf the total the buildings,number of as documented well as the surrounding tomb elevations constructions in the Middle where the Guadiana, production we areasmanaged would to examine be located, a total is something of nine using that the is APSFR quite controllable. methodology All proposed the examples in this underpaper: study are located outside the T10 events, while still being located close to the land affected by these floods, allowing the buildings to control areas of fertile land for agricultural development (Figure 17).

Remote Sens. 2021, 13, 3506 21 of 29

Cancho Roano, La Mata, Las Lomas and Lácara, as they are four enclaves located in the interior of the Guadiana, next to one of its tributaries, but far from the main artery of the Guadiana. As we do not have predictive models to evaluate the areas with potential flood risk in the cases corresponding to the tributaries of the Guadiana, we do not have sufficient information to evaluate the spatial relationship between them and their nearby watercourses. The application of the APSFR data to the DTMs generated after the processing of the LiDAR flights allowed us to make some very interesting observations. First of all, it should be noted that all the elevations are safe from the events that occur every 10 years. This is quite logical, because if we take into account that the approximate lifespan of these buildings is about 100 years on average, preventing the floods that occur every 10 years from affecting the buildings, as well as the surrounding constructions where the production areas would be located, is something that is quite controllable. All the examples under Remote Sens. 2021, 13, 3506 study are located outside the T10 events, while still being located close to the land affected20 of 28 by these floods, allowing the buildings to control areas of fertile land for agricultural development (Figure 17).

FigureFigure 17.17.Models Models obtained obtained from from the the APSFR APSFR analysis analysis of of the the tumuli tumuli of Huertaof Huerta de Donde Don Mateo Mateo (Talavera (Tala- vera la Real, Badajoz, Spain) (A) and Casas del Cerro de la Barca (Badajoz, Spain) (B) showing the la Real, Badajoz, Spain) (A) and Casas del Cerro de la Barca (Badajoz, Spain) (B) showing the location location of the buildings with respect to the three flood events. of the buildings with respect to the three ﬂood events.

Only one of the examples seems to have been affected by the T100 event. This is the tumulus of Cañada la Virgen (Puebla de la Calzada, Badajoz, Spain) (Figure 18), one of the enclaves most affected by modern-day agriculture, as due to the Badajoz Plan, this site has been completely razed, which is why the results obtained in this analysis have raised some doubts, given the alteration that both the site and its surroundings have suffered. In contrast, there are several examples which are either not affected by any of the events, or which are only affected by T500 events, which, given the lifespan of these buildings, could not possibly be controllable or predictable. We can point out examples such as the tumuli of Turuñuelo de Villagonzalo or Casas del Turuñuelo, which would have been submerged under the waters of the Guadiana in events occurring every 500 years (Figure 19). Remote Sens. 2021, 13, 3506 22 of 29

Only one of the examples seems to have been affected by the T100 event. This is the tumulus of Cañada la Virgen (Puebla de la Calzada, Badajoz, Spain) (Figure 18), one of the enclaves most affected by modern-day agriculture, as due to the Badajoz Plan, this site has been completely razed, which is why the results obtained in this analysis have raised some doubts, given the alteration that both the site and its surroundings have suffered. In contrast, there are several examples which are either not affected by any of the events, or which are only affected by T500 events, which, given the lifespan of these buildings, could Remote Sens. 2021, 13, 3506 not possibly be controllable or predictable. We can point out examples such as the 21tumuli of 28 of Turuñuelo de Villagonzalo or Casas del Turuñuelo, which would have been submerged under the waters of the Guadiana in events occurring every 500 years (Figure 19).

FigureFigure 18.18. ModelModel obtainedobtained fromfrom thethe APSFRAPSFR analysisanalysis ofof thethe areaarea wherewherethe thetumulus tumulusof of Cañada Cañadala la Virgen (Puebla de la Calzada, Badajoz, Spain) is located, showing the effect of events T100 and T500 Virgen (Puebla de la Calzada, Badajoz, Spain) is located, showing the effect of events T100 and T500 on the site. on the site.

AtAt thethe VillagonzaloVillagonzalo site, site, no no archaeological archaeological work work has has been been carried carried out out to to date date to toverify verify thethe existenceexistence ofof stratigraphicstratigraphic unitsunits thatthat cancan bebe identifiedidentified withwith floodingflooding events.events. However,However, thethe workwork atat thethe tumulustumulus ofof CasasCasas deldel TuruñueloTuruñuelo hashas provided provided evidenceevidence thatthat itit hashas beenbeen affectedaffected byby floodingflooding events events that that have have lasted lasted for for a a considerable considerable period period of of time. time. Evidence Evidence of of thisthis hashas beenbeen foundfound inin thethe southernsouthern profileprofile of of the the tumulus, tumulus, where where a a sequence sequence of of sediment sediment depositsdeposits mademade by the the river river in in the the years years following following the the concealment concealment of the of thebuilding building has been has beendocumented, documented, and in and the insequence the sequence of the ofcourtyard, the courtyard, where there where is thereevidence is evidence of a flooding of a floodinglevel beneath level beneaththe ritual the deposit ritual depositof animals of animals that is currently that is currently being analysed being analysed using micro- using micromorphology,morphology, to determine to determine its chronology its chronology and scale. and The scale. fact The that fact we thatnow wehave now evidence have evidencethat allows that us allowsto assess us the to assesseffect that the the effect river that itself the may river have itself had may on havethese hadconstructions on these constructionsleads us to begin leads a usnew to line begin of awork new lineon the of workcauses on that the led causes to these that ledstructures to these being structures aban- beingdoned abandoned and sealed. and sealed.

Remote Sens. 2021, 13, 3506 22 of 28 Remote Sens. 2021, 13, 3506 23 of 29

FigureFigure 19.19.Models Models obtainedobtained fromfrom thethe APSFRAPSFR analysisanalysis ofof thethe tumulitumuli ofof ElEl TuruñueloTuruñuelo (Villagonzalo,(Villagonzalo, Badajoz, Spain) (A) and Casas del Turuñuelo (Guareña, Badajoz, Spain) (B) showing how the T500 Badajoz, Spain) (A) and Casas del Turuñuelo (Guareña, Badajoz, Spain) (B) showing how the T500 event affected both the buildings and their surrounding land. event affected both the buildings and their surrounding land.

5.5. DiscussionDiscussion TheThe historicalhistorical analysis analysis of of thethe landscapelandscape inin regionsregions suchsuch asas thethe middlemiddle GuadianaGuadiana basin,basin, whichwhich hashas beenbeen greatlygreatly alteredaltered byby thethe impactimpact ofof agricultural agricultural work,work, hashas always always entailedentailed greatgreat difficulties.difficulties. TheThe orographyorography andand landscapelandscape of of these these territories territories is is so soseriously seriously affected affected thatthat reconstructingreconstructing theirtheir originaloriginal morphologymorphology is,is, inin many many cases, cases, an an impossible impossible task. task. The The transfertransfer ofof land,land, thethe redistributionredistribution ofof plotsplots and, and, above above all, all, the the levelling levelling to to which which many many of of thesethese fields fields have have been been subjected,subjected, has has ledled toto thethe lossloss ofof valuable archaeological information,information, especiallyespecially that that which which corresponds corresponds to to the the so-called so-called peasant peasant settlements, settlements, since, since, in contrastin contrast to theto the Tartessian Tartessian buildings buildings hidden hidden under under tumuli, tumuli, the scarcity the scarcity of their of material their material and architectural and archi- remainstectural meansremains that means the archaeologicalthat the archaeological footprint footprint they leave they on leave the territoryon the territory is very is small very andsmall easily and destroyed.easily destroyed. InIn responseresponse toto this, this, through through archaeology archaeology and and landscape landscapeanalysis, analysis, wewe seek seek tools tools that that willwill help help us us to to restore restore a territorya territory to itsto originalits original appearance, appearance, the structurethe structure it would it would have have had priorhad prior to the to impact the impact that agriculture that agriculture has had has on had its on configuration, its configuration, and on and the on conservation the conser- ofvation the sites of the in itssites surroundings. in its surroundings. This is theThis case is the of thecase methodology of the methodology used in theused present in the present study, through which we intend to identify the activity that the Guadiana River

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study, through which we intend to identify the activity that the Guadiana River has had throughout its history and how this activity has affected the sites located in its immediate surroundings, to the point of conditioning the development of its activities or determining the moment of abandonment of the sites. To do so, we used historical photography and LiDAR to identify the presence of paleochannels or old branches of the Guadiana that were in operation in the past, possibly prior to the regulation process that affected the river due to the construction of the reservoirs. However, this analysis of the river network does not allow us to address the relationship between the river and its settlements. For this reason, we have searched for a tool to help us simulate flood patterns. In this way, overcoming contemporary obstacles such as the tomb elevations, the terraces or the plots sown with maize, we can determine how the settlements were affected by the flooding of the Guadiana in events occurring every 10, 100 or 500 years. In light of the results obtained, we can confirm the usefulness of the methodological proposal contained in this work. Thanks to it, and despite the fact that it is not an absolute model, and that within it and depending on each geographical region, different variables must be taken into account, we have managed to configure the most realistic possible image of the structure that the middle Guadiana basin would have had in antiquity, using this as the basis to analyse the relationship between the river, the areas for exploiting resources, and the different settlements. Perhaps the first idea to be drawn from this study is the importance of reconstructing the palaeolandscape, as analysing the location of sites using the current landscape as a reference point can result in a number of errors. This is especially the case in regions such as the middle Guadiana basin, where the human impact on the territory is so significant that many of the sites under study have lost their connection or relationship with the territory. For this reason, it is necessary to define the original route of the river or to identify river arteries that are currently silted up, which in ancient times must have played a fundamental role in the organisation of the territory and in the choice of areas for building settlements. Leaving aside the territory in which the necropolises are located, the application of this methodology has made it possible to corroborate the relationship that existed between the settlements of the first Iron Age and the Guadiana River. The position occupied by both the settlements on the plains of the village or farm type, and the Tartessian buildings hidden under tumuli in the territory, close to the watercourses and, mainly, to the areas affected by the flooding of the rivers, allows us to consider the fundamental role that the waterways played in the political and economic organisation of the territory. In addition to controlling the passage of one of the main communication arteries, the Guadiana, the proximity to the lands affected by the floods made it possible to control the most fertile plots, those that were periodically affected by the floods, which led to an increase in the productivity of the land. This model is by no means exclusive to this territory and is widely attested in other parts of the Mediterranean. The analysis of the resulting cartography allows us to observe how all the sites documented to date are outside of the T10 events, which reveals the knowledge that the societies that inhabited this area between the seventh and fifth centuries BC had of their surroundings. Given that these are events that occur every ten years, control over them would have been more effective. This would allow the sites to be located at a sufficient distance to prevent the floods from affecting the buildings, while at the same time leaving the fertile land near the riverbed under their control. In this way, the height/width represented in the T10 events can be interpreted as the space within which the course of the river would have been located during antiquity, prior to the regularisation of its course; in other words, the shading that the T10 event occupies in the models corresponds to the zone through which the course of the river may have potentially run, differing from the current one. This idea does not mean that in the past, the river occupied the entire width that the T10 shading shows in the models, but rather that this width defines the maximum limits that the river would have reached and the space through which its course was Remote Sens. 2021, 13, 3506 25 of 29 Remote Sens. 2021, 13, 3506 24 of 28

limits that the river would have reached and the space through which its course was di- diverted.verted. This This can can be be corroborated corroborated by by superimp superimposingosing the T10 event layerlayer onon thethe historicalhistorical photographphotograph priorprior toto thethe constructionconstruction ofof thethe reservoirsreservoirs andand thethe currentcurrent orthophotography,orthophotography, wherewhere thethe narrowingnarrowing ofof thethe riverriver cancan be be detected. detected. ToTo illustrate illustrate this this idea, idea, we we selected selected one one stretchstretch of of the the river river between between the the towns towns of of Medell Medellínín and and Don Don Benito/Villanueva Benito/Villanueva de de la laSerena Serena (Badajoz,(Badajoz, Spain), Spain), as as it it contains contains a a large large number number of of sites sites (Figure (Figure 20 20).).

FigureFigure 20.20.Cartography Cartography resultingresulting fromfrom superimposingsuperimposing the the T10 T10 shading shading on on a a photogram photogram of of the the AMS AMS (B) (1956–1957) (A) and a photogram of the most recent PNOA (B) to observe the impact that the (B) (1956–1957) (A) and a photogram of the most recent PNOA (B) to observe the impact that the execution of the Badajoz Plan had on the course of the river. execution of the Badajoz Plan had on the course of the river.

TheThe knowledgeknowledge possessedpossessed byby thethe societiessocieties thatthatinhabited inhabitedthis thisarea area in in antiquity antiquity about about thethe eventsevents thatthat occurredoccurred every 10 10 years years also also s seemseems to to be be in in relation relation to to the the T100 T100 events, events, as aswe we only only have have one one case case study, study, the the tumulus tumulus of of Cañada Cañada la la Virgen (Puebla(Puebla dede lala Calzada,Calzada, Badajoz,Badajoz, Spain),Spain), affectedaffected byby this this event. event. InIn contrast,contrast, the the degreedegree of of impact impact exerted exerted by by events events occurring occurring every every 500 500 years years is is much much greater,greater, whichwhich hashas allowedallowed usus toto draw draw up up a a set set of of hypotheses. hypotheses. GivenGiven thethe chronological chronological extent of these events, which occurred every 500 years, it is coherent to think that the

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inhabitants of the different enclaves or settlements were not able to predict the arrival of these events or floods. If we refer to the chronologies in which the sites of the first Iron Age are active in the middle Guadiana basin, it is true that, with the exception of Cancho Roano, which has several phases of occupation, it seems that the rest of the enclaves were only in use between the sixth and fifth centuries BC, so that their activity does not seem to exceed two centuries. Therefore, predicting or avoiding flood damage every 500 years would not have been easy.

6. Conclusions By applying this methodological model to a specific territory, such as the middle Guadiana basin, and to a specific chronology, the first Iron Age (seventh to fifth century BC), a series of historical conclusions can be drawn that help us to interpret the settlement of this region during its protohistory. This is the ultimate goal of our work: to extrapolate spatial data to a historical reality in order to assess how the physical environment has conditioned the development of human activity. Given that the study carried out concerns various categories of settlement, there are several interpretations that can be drawn from this study. Nevertheless, it is true that the sample we have available to analyse the location of village or farm settlements is too small to draw general conclusions; however, the location of the Cerro de la Barca—Torruco site reveals the interest in these enclaves regarding their location near watercourses with the aim of exploiting the fertile land left in their wake, as well as in using them as communication routes for the transport of goods. As far as the necropolises are concerned, the application of APSFR data has allowed us to confirm the relationship between watercourses and the location of these funerary spaces [43]. The analysis of all the known cases has confirmed the presence of a watercourse that separates the necropolis from the settlement with which it would have been connected. This evidence is not exclusive to the middle Guadiana, but dates back in time to the Phoenician necropolises both in the east and west [44], and is also present in the Tartessian necropolises of the Guadalquivir valley [45]. Detecting this pattern in the Guadiana basin confirms the survival of a tradition, the roots of which go back to the arrival of eastern populations in the Iberian Peninsula. However, undoubtedly the most significant data are derived from the spatial analysis of the territory occupied by the Tartessian buildings hidden under tumuli. In this sense, one of the debates still pending in the research on this type of settlement refers to why these structures were suddenly abandoned and concealed at the end of the fifth century BC. This was an event that occurred at the same time as all the constructions, resulting in a massive abandonment of this area, the middle Guadiana basin, which remained practically uninhabited until the arrival of the Romans. Traditional literature has sought an explanation for this exodus in the arrival of populations from the north, specifically of Celtic origin [46]. However, archaeology shows that the sealing and concealment of these structures would have taken days of work and required the help or collaboration of a large part of the surrounding population. It is therefore inconceivable that under the pressure of a siege or conquest, such a task could be carried out. It should also be remembered that in examples such as Cancho Roano or Casas del Turuñuelo, the sealing of the buildings was accompanied by a ritual that included a mass sacrifice of animals, which requires even more time to be carried out; a ritual that fits perfectly with the occurrence of an environmental catastrophe. It is also striking that remains of weapons, or evidence of looting or violence were found in none of the contexts analysed, which undermines the hypothesis of pressure from populations from the Meseta. For some time, we have considered the possibility that a change in climate, possibly in the rainfall pattern, caused these settlements to be abandoned, and their populations to move to other parts of the Iberian Peninsula. However, the application of this APSFR methodology has allowed us to add another cause or hypothesis that we will have to corroborate with the help of disciplines such as microstratigraphy and carpology. This Remote Sens. 2021, 13, 3506 26 of 28

refers to the possible effect that the T500 event had on these structures, corroborated in examples such as the site of Casas del Turuñuelo, in whose lower courtyard the remains of a flood have been documented, over which animals were sacrificed prior to the building being sealed [47]. As the life span of these structures was around a century between the sixth and fifth centuries BC, we can assume that the societies who occupied these buildings were able to predict events occurring every 10 to 100 years, but not to calculate events occurring every 500 years. This leads us to suppose that one of these events caused the collapse of the territorial system, forcing these populations to abandon their buildings and move to other parts of the Iberian Peninsula, putting an end to the territorial model of this region during the first Iron Age. The power that these constructions held and their symbolic importance led their inhabitants to conceal them and protect them from looting or destruction, allowing many of them—those unaffected by agricultural work—to reach us in an excellent state of preservation.

Author Contributions: Conceptualization, E.R.G., P.P.D. and S.C.P.; methodology, E.R.G. and P.P.D.; software, P.P.D.; validation, E.R.G. and P.P.D.; formal analysis, P.P.D.; investigation, E.R.G. and S.C.P.; resources, E.R.G., P.P.D. and S.C.P.; data curation, E.R.G. and P.P.D.; writing—original draft preparation, E.R.G.; writing—review and editing, E.R.G., P.P.D. and S.C.P.; visualization, E.R.G. and P.P.D.; supervision, S.C.P.; project administration, S.C.P.; funding acquisition, S.C.P. All authors have read and agreed to the published version of the manuscript. Funding: This works has been partially supported by the research project “Construyendo Tarteso 2.0. Análisis Constructivo, Espacial y Territorial de un modelo arquitectónico en el valle medio del Guadiana” (PID2019-108180GB-100) funded by the Spanish Ministry of Science and Innovation. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results. Data Availability Statement: The base cartography used for this study in available at the following web links: http://www.ign.es/web/ign/portal (accessed on 3 September 2021) and http://ideex.es/ Geoportal/pages/ideex (accessed on 3 September 2021). Acknowledgments: The authors would like to thank the reviewers for their valuable feedback on an early draft of this manuscript. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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