Lasanté des paysages devrait peut-être être mesurée en fonction de leur degré d'intégrité. Par exemple, l'intégrité de l'environnement total d'un paysage historique, y compris son tissu social et physique, peut être une bonne mesure de la santé, mais ce n'est pas simple en pratique. Le paysage sacré de Lalibela, inscrit au patrimoine mondial, subit depuis plusieurs siècles desmenaces d'origine humaine et naturelle qui ont modifié les schémas initiaux d'utilisation des terres. Cet article identifie deux défis cruciaux en matièrede gestion du paysage en se basant sur une étude de cas qui a utilisé uneenquête de terrain, une documentation photogrammétrique et une analyse desources secondaires. Il suggère une politique visant à restaurer le modèle d'utilisation des terres et les systèmes de drainage d'origine en tant questratégie de renforcement de la résilience face aux éventuels impacts futurs duchangement climatique.
The health of landscapes should perhaps be measured through the degree of their integrity. For example, the integrity of the total environment of a historical landscape, including its social and physical fabric, can be a good measure of health, yet this is not simple in practice. The world heritage sacred landscape of Lalibela has for several centuries experienced man-made and natural threats which have modified the original land-use patterns. This paper identifies two critical landscape management challenges based on a case study that employed field survey, photogrammetric documentation and secondary source analysis. It suggests a policy towards restoring the original land use pattern and drainage systems as a strategy for building resilience against possible future climate change impacts.
The health of landscapes should perhaps be measured through the degree of their integrity. For example, the integrity of the total environment of a historic landscape including its social and physical fabric can be a good measure of health and yet this is not simple in practice because appropriate conservation strategy necessitates clearly understanding and defining what a particular cultural landscape is.
The conservation of the sacred landscape of Lalibela in Ethiopia, for example, has led to the conflicting goals of conserving the authentic fabric and relocating a portion of the community that continually lived for centuries. This action has indeed modified the original land use pattern and affected the ‘health’ of the historic public space. Such management challenges have in fact a lot to do with the very the definition of the authentic aspects of the landscape fabric and its development. Exemplary cases include urban heritages that are increasingly being commoditised for tourism or promoted for rapid development ( ICOMOS, 2011; Martínez, P.G., 2017; Orbasli, 2000; Orbasli, 2017; Sykes & Ludwig, 2015).
In addition, there are always local challenges that may not be identified clearly. Understanding the history and traditions of landscapes is a necessary component of sustainable heritage conservation as recommended by the 2011 Historic Urban Landscape (HUL) approach for dealing with local challenges of landscape definition, conservation, and management ( ICOMOS, 2011; Plieninger & Bieling, 2012; World Heritage Centre, 2011).
Famous as a world heritage site since 1978, the core of the historic town of Lalibela is a sacred landscape comprising of eleven highly decorated monolithic churches built as rock-hewn structures in a massive geological framework. Known as Dabera Roha (Mount Roha) prior to the twelfth century AD, the town was later called as Lalibela after the king who had designed and or modified the landscape, according to legend. The sacred landscape of Lalibela has experienced man-made and natural threats which have modified the original land use patterns and landscape features for several centuries. One notable is the16th century Gragn War. Being archaeological, architectural and cultural landscape of large scale, the wellbeing of the sacred landscape, therefore, depends so much on how its authenticity should be defined and how its integrity should be managed. In this regard, this paper has identified two critical management challenges related to its integrity and future resilience.
A case study methodology was employed that involved field survey, photogrammetric documentation and secondary source analysis. The field survey incorporated two expeditions. The first one was carried out in 2016 and was already reported as “Columbia, U. (2017). Heritage, Tourism, and Urbanization: the Landscape and Development of Lalibela”; and the second one took place in 2019 primarily aiming at the photogrammetric documentation of selected rock-hewn structures including unstructured interviews with key stakeholders. Secondary sources were additionally consulted to clarify certain issues that could not be covered through the field survey. The3D photogrammetric documentation project generated digitally rendered images and orthogonal projections of architectural views for better understanding of the landscape and assessment of the previous conservation interventions. The photogrammetric recording was conducted through hand cameras. Except the Church of Biete Medhane Alem, which is too huge to acquire quality images through hand cameras, all the free standing monolithic churches were externally recorded and architecturally documented. Additionally, the main façade of Church of Biete Libanos was recorded. Then, an application program called Agisoft PhotoScan Professional was used to produce the renderings and orthogonal projections.
No adequate effort has been exerted for the research and documentation of the Lalibela landscape and its rock-hewn churches despite the recognition as a world heritage for more than four decades (Ruther and Palumbo, 2012), and its first exposure to international restoration intervention since the early 20th century when a restoration project was commissioned by the Empress Zewditu (Columbia,2017: 24). Though there was a considerable effort in the 2009 Zamani documentation project for the 3D laser scanning of the general site by the University of Cape Town (Columbia, 2017:10; 41;Ruther and Palumbo, 2012), there is a need for further documentation and research on particular architectural and engineering components because the effectiveness of landscape management plans rely on sufficiently understanding the complexity with the design context and pattern of the monolithic churches. Itis already noted that:
“Churches, tombs,and catacombs carved out of volcanic tuff rock have been built in a variety of styles and methods including chiseling them top-down into the face of the rock or hewing them as isolated standing blocks. A complex and extensive system of drainage trenches, tunnels, and subterranean passageways connects the underground structures, doubling as circulation routes…The roofs of the four free standing monolithic churches slope at the same angle of the rocks from which they were carved, further promoting drainage” (Mercier 2012,47–66, cited in Columbia, 2017: 34).
Because sustainable conservation requires more precise drawings for understanding of the particular pattern of the landscape, one area of research and documentation that requires adequate coverage is the ruling out of the design pattern and context of the original landscape. For example, a careful observation of the photogrammetric 3D rendering of the Churches of Biete Mariyam (Fig. 1 and 2), and Biete Giorgis(Fig. 4) indicate evidence of ancient wisdom on site context adaptation through the optical correction mechanism. This can also be confirmed by the façadeof Biete Amanuel (Fig. 6) which in contrary maintains a geometric rigidity due to the plainness of its surrounding cave. Still, much is not known on the ratio and proportioning system of the Lalibela architectural style.
In addition to the need for precise and complete generation of technical digital images and drawings, the incorporation of artistic impression in digital heritage documentation and analysis should be encouraged. This is because renderings with accentuated effects may be easier for visualization of a structure and appreciation of its genus loci. Some examples are illustrated in Fig 3, 5, and 7.
The general public of Lalibela, who are followers of the Ethiopian Orthodox Christianity, as indigenous inhabitants, has been using the sacred landscape of the town for spiritual, ceremonial, residential and commercial land uses for several centuries.
Such traditional land use patterns were common in most townscapes of the northern part of medieval Ethiopia (Garretson, 2000; Gebregiorgis, 2011). Fig 8 illustrates an example of a typical medieval townscape of Ethiopia. However, a notable aspect of the traditional land use pattern of the Lalibela sacred landscape is that the three groups of churches comprised complex underground rock-hewn architectural and engineering system connected through tunnels and hydrological trenches (Fig. 9 illustrates an example of this complexity with a simple site section diagram). Then, the traditional two story circular cottages made of stone brick and mud with thatched roof, referred locally as the Gojo, surrounds the rock hewn churches, sometimes connected with the churches through tunnels. The market and the openspaces including the ceremonial spots had been easily accessible by residents from their Gojo areas or the neighbourhood. This traditional land use pattern is now endangered and a survey shows (See Fig. 10) that only a few Gojo houses are now inhabited by people due to a relocation program funded by the World Bank (Columbia, 2017: 52, 73-96). Despite the strong justification provided for this relocation project and the need for their settlement of the surrounding community, there should have been proposed a strong mitigation plan for the post execution phase of the project. This gap can impact the preservation of the intangible heritages and traditional values, the security of movable treasures kept inside the churches, and the vibrancy of the traditional public space.
In addition to this modification of the traditional land use pattern, the tunnels and hydrological drainage systems of the historic landscape are endangered due to two main reasons: First, their original network is not very well understood and thus could not be completely restored (Fig.10 illustrates the possible location of buried tunnels and trenches). As mentioned in the previous section, this could be solved through a precise and complete documentation of the site.
Second, there are problems associated with the location of the heavy supporting structures of the shelters over the four churches and their effectiveness for preventing rainfall and harsh sunlight. For example, one of the supporting pillars of the shelter of Biete Amanuel is located over the top of an underground tunnel which is said to be developing cracks by the locals. The local community has mostly argued against the use of the shelters. In fact, from the get go, the locals were concerned about the heavy shelter structures when one structural element fell over the roof of the church of Biete Medhane Alem. Then, there was a protest by the locals to stop the construction project; the protest was brought under control by governmental forces, according to local sources, adding that there had been no satisfactory public participation regarding the conservation projects from the beginning. In fact, an earlier technical report on the inspection and evaluation of the shelters (Asrat and Gebreyohannes, 2014) concludes that the shelters are not stable and will intensify water infiltration, weathering and decomposition of surfaces in the long run in addition to their heaviness endangering underground structures. Fig. 11 illustrates an example of a heavy support base.
The field observation also indicated that cave erosion has been causing the deterioration and cracking of the monolithic surfaces of the Biete Gebriel-Rufael church complex. This is most probably due to the increase in flooding amount in the rainy seasons. Temperature increase in the summer may have also speeded up evaporations. Either the inappropriate conservation measures or climate change can be the cause. In any case, the wise restoration of the original land use pattern and the full integrity of the original hydrological systems are important to mitigate such adverse effects which will probably be severe in the future. The earlier excavation of buried trenches by Angelini(1967) in the 1960s has remained without progress. Perhaps, this suggests for proposing for new excavation projects as a mechanism to build future resilience against climate change impacts.
Inadequacy of digital documentation and the previous inappropriate conservation measures are critical challenges for the ‘health’ of the Lalibela historic landscape. The first has challenged capacity building for resilient landscape planning and management of Lalibela; and the later has endangered the safety of historic sites in several aspects. Such critical challenges affecting the integrity of Lalibela may determine its ‘health’.
As shown with the photogrammetric 3D renderings, understanding the ancient wisdom of design context adaptation and the proportioning system of the design pattern require further documentation and research including the monitoring of the cave erosion, and mapping of the network of trenches and tunnels that may be restored and reused. Artistic impression in digital heritage documentation should also be encouraged. In addition, a broader and critical evaluation of previous conservation interventions should be conducted to reconsider the modification of traditional land use pattern and the sheltering mechanism of the churches. This paper suggests the restoration of the total integrity of the landscape as a strategy to mitigate climate change impacts that will probably be severe in the future. In this regard, the complete excavation and reuse of the hydrological trenches and tunnels may help to control flooding and can minimize cave erosion.
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All images are by the authors.