Geophysical Prospection and Aerial Photography
The traditional technique of excavation, while providing valuable insights into many aspects of life in the medieval capital of Alwa did not significantly increase our knowledge about its spatial organisation. Surface surveys, cleanings and mapping, while delivering some information, remain difficult to interpret. The mounds are visible markers of ruined buildings and complexes but no complete architectural remains protrude from the ground. Only debris such as red bricks, mud bricks and small finds can be spotted on the surface. Based on such scarce information, it is difficult to build a strategy for the protection and management of the site, especially with accelerating development in the region (Figure 5). If no action is taken to protect it, soon the rest of Soba will be affected by modernisation.
In these circumstances, a new approach needs to be developed. Since medieval architectural remains are just below the sandy surface of the site, the most reasonable method for their identification is a geophysical survey. However, this method has never been used in Soba. Before launching a large-scale project, it was essential to confirm that the method is suitable for the local conditions.
In January 2018, with the approval of Dr Abdelrahman Ali Mohammed (General Director of the NCAM), initial research was conducted in Soba by the authors (Drzewiecki and Ryndziewicz 2018: 33–34).
For the geophysical measurements, magnetometry was chosen as the most suitable for an initial survey. As an expeditious and non-invasive method, magnetometry offers effective way to collect the data and is able to detect and identify a wide assortment of archaeological features (David et al. 2008: 20–21). Due to the magnetic properties of alluvial Nile sediments, the magnetic method is highly effective in surveying the archaeological remains in Sudan and Egypt (Herbich 2019: 197).
A small area (80 × 40 m) was selected for geophysical test-measurements (Figure 6). The area included the top of one of the mounds, its slopes and the surrounding flat terrain. No medieval architectural features were visible on the surface of the study area, a common situation in Soba. A Geoscan Research FM 256 fluxgate gradiometer was used to measure the gradient of the vertical component of the Earth’s magnetic field with a resolution of 0.1 nT. Measurements were taken with a sampling density of eight readings per 1 m2 (every 0.25 m along profiles 0.5 m apart) within the 20x20 m grid.
To visualise the result, a grey-scale plotmap was created (Figure 7). Geoscan Research Geoplot 3.0 software was used to elaborate the data, following the essential set of processing techniques. Despike algorithm was used to minimise the influence of possible small iron detritus. The inaccurate positioning of particular profiles due to the use of zigzag mode was adjusted by the Destagger function. Zero Mean Traverse, Interpolation (to 0.25 × 0.25 m) and Low-Pass Filter were applied to normalise the contrast and smooth the appearance of anomalies. The resulting image shows various types of linear and dot-shaped anomalies that can be interpreted as a geophysical reflection of remains of urban structures.
To understand the nature of particular geophysical anomalies, we considered the results of other magnetic surveys, done at a larger scale in the Middle Nile Valley, particularly at Meroe (Mohamed Ali et al. 2012) and Hamadab (Ullrich and Wolf 2015). Although those projects do not concern medieval settlements, the geomorphological conditions and building materials were similar. The explanation of the relationship between anomalies measured and buried structures is based also on the archaeological features and findings known from the excavations carried out at Soba in the past. According to the results of the excavations, most of the buildings in Soba were constructed of mud brick (Welsby and Daniels 1991: 26). Red brick walls were preserved in a poor condition, and most of them were recorded as negatives since the bricks had been removed. Also many disturbed layers and concentrations of scattered red brick debris were recorded in the course of the excavations (Welsby and Daniels 1991: 29).
Magnetic imagery shows regular, low amplitude, linear anomalies that can reflect mud brick walls. These potential walls are slightly angled from the magnetic north. Similar orientation of buildings was observed in some of the architectural remains discovered by Welsby and Daniels on kom B (Figure 8). A high level of noise was recorded across most of the study area, probably due to unstructured red brick debris just below the surface. Excavations in Soba delivered material related to metalworking (Freestone and Stapleton 1998: 81). Based on this evidence, it might be estimated that some spots of large, high-amplitude anomalies are connected with ash deposits or slag. Heavily burnt material may cause anomalies similar to iron fragments. Because of this, any definitive interpretation of the anomalies is not possible without further investigation.
Although the area examined by magnetometry is relatively small, this sample demonstrates the usefulness of the method. It can be assumed that extending the area of the survey will provide crucial information concerning urban planning, as well as the spatial pattern of architecture at Soba (Figure 9). Remains of architecture were recorded on the top and slopes of the mound, as well as in a part of the flat area. This last observation is very important, as it gives an opportunity to study the building distribution on the flat areas between the mounds.
The same study area was documented with a camera suspended under a drone. A series of 228 aerial photographs were taken. Subsequently, the photographs, supplemented by six GPS-measured ground control points, were used to create a 3D model of the surface by means of Agisoft Photoscan software. Three-dimensional data allowed for the creation of a digital elevation model which was transferred to QGIS software (Figure 10), where it could easily be overlapped with the map of anomalies, since both are done in the framework of the same coordinate system (WGS 84). This method of documentation provides detailed data on the topography of the area under investigation. It is suitable for tracing and documenting artificial mounds (koms) which are abundant at Soba. At the same time, when overlapped with the magnetic map it enabled a better understanding of the anomalies visible in the results of the geophysical prospection.
In conclusion, preliminary research conducted in January 2018 gave interesting results, suggesting that a combination of aerial photography and geophysical survey is an approach which can be an efficient method to better understand the archaeological landscape of Soba. A map presenting potentially buried archaeological structures can also become one of the tools in developing protection strategies for the site.
Working with the Community
Approximately, 220 ha of the medieval capital is now being densely overbuilt or covered with fields, 80% of the estimated site size. This is a relatively new situation. Analysis conducted in June 2018 of satellite imagery allows for a conclusion that private houses have been built over large parts of the site during this century (Figure 11). When Derek Welsby (personal communication) was conducting his research in the 1980s and 1990s, the area was sparsely populated and the hamlet closest to Soba consisted of a few houses. Today, large amount of people is living in the area.
On the one hand, present-day residents may still remember settling in Soba and may be in possession of artefacts found during various activities, ranging from house construction to common activities in the fields and around their homes. On the other hand, the old Sudan Survey Map of the Khartoum region (sheet 55-B) indicates that already in 1916, there was a small settlement in the area. How far back does it date? Do families living in the oldest part distinguish themselves from more modern residents? Do they keep oral traditions and stories connected with the remains of the capital?
Working in cooperation with the local community is an obvious step in this context. It is important to find common objectives which can constitute goals for the researchers and the residents as well. Both groups should have voices which will express their expectations. Various views taken into consideration and pursued should increase the chances for a long-lasting cooperation. Since the researchers are a small and specialised group, their voice is more homogenous, focused on research, protection of the remains and the work that they are set to conduct. More challenging is to obtain accurate data from a much larger and more varied group of residents. Their approach can depend on multiple factors, connected with their jobs, everyday life and the ways they understand the history of the region.
An interesting case study was made in 2014 and 2015 in the Meroe region, approx. 200 km north of Soba (Humphris and Bradshaw 2017). There, a quantitative method of questionnaire survey was used to determine local expectations and knowledge about the ruins of Meroe and general understanding of archaeology. This was the first time in Sudan when such a method was used for archaeological heritage studies. Responses were obtained from 215 persons, bringing interesting insights and ideas.
Despite more than a century-long history of archaeological research in Meroe, 13.75% of interviewees did not know what archaeology is and an additional 14.17% of respondents did not provide an answer to the question. For the question about the remains of Meroe, 23.74% of interviewed stated that they did not have any knowledge on the subject. This information seems shocking since the remains of Meroe cover a large area surrounded by modern settlements. The ruins are easily visible and the numerous pyramids are one of the country’s symbols, used in nationwide media (television and newspapers).
The results provided by the questionnaire survey at Meroe are paralleled by information collected during a community archaeology project conducted on Mograt Island in 2014–2016 (Tully 2014, 2015; Tully and Näser 2016). Mograt is the largest island on the Nile, located approximately 450 km north of Soba and 250 km north of Meroe. The methodology in the project was different from the one implemented in Meroe. It was based on archaeological ethnography (Castañeda and Matthews 2008) and public archaeology (Marshall 2002; Merriman 2004). The approach was more qualitative than quantitative, based on individual interviews and community consultations.
The result revealed a large interest in archaeology and history while at the same time, a lack of information about these issues was recognised. Researchers noted that information about research and the regional past are not easily available for the residents. In conclusion, at the end of the project and in consultation with local people, a publication was prepared in English and Arabic bridging identified gaps (Tully and Näser 2016). The target reader was schoolchildren since they constituted the largest age group in the region. The book was printed and distributed in schools and among the residents as well as made available online (http://www.mogratarchaeology.com/sites/default/files/2018-11/MogratBook_WebVersion.pdf, accessed on 13 March 2019).
In the case of research at Soba, creating a comfortable environment for a questionnaire survey will be challenging. The Meroe team had been working for ten seasons at the time when the survey was developed (Humphris and Bradshaw 2017: 204). The residents knew the researchers and at least some of them participated in joint fieldwork. In Soba, we will be the newcomers. At the beginning, we may come across hesitation and lack of trust which might become obstacles in communication. That is why a qualitative approach similar to the methodology used on Mograt Island will be applied for the first seasons of fieldwork at Soba.
To find, contact and identify common ground with the residents, an individual approach with unstructured and semi-structured interviews will be applied. Since our research team will be living in a rented house next to the site, everyday contacts will be a good possibility to talk and to start getting to know the residents. Simultaneously, meetings with local authorities, people’s representatives and local associations will be organised. The main agenda of the meetings will be to introduce ourselves and create an open atmosphere for discussion about the remains of Soba. After obtaining permissions, visits to local schools will also be arranged.
In December 2018, a second journey to Soba was made with the aim to test the potential for cooperation with the local community and to document modern activities on the site, using aerial photography. At that time, the local police station was visited and a meeting with the police chief organised. One of the policemen guided us to a modern household on the site, where the most recent accidental discovery was made. The house owner was surprisingly open, and we were shown remains of red brick, mud brick and stone architecture protruding from the ground in the courtyard (Figure 12). We were informed that recently a large pottery vessel was discovered at the place, with bones inside. The landowner stated that it looked like a child interment.
He did not keep the finds but passed them to the local authorities. The policeman, however, did not have any information about the objects. In the future, the residents will be making more of this sort of chance finds. This is why clear and easy guidelines and procedures should be established and promoted in the community and among the authorities, to have as much information as possible reaching the researchers and authorities responsible for the safekeeping of the site.
A few students and graduates of archaeology from Al-Neelain University (our research partner) live in the Soba area. During the second visit to the site, we were joined by two of them and were able to meet with one other, living approximately 600 m from the site. They were open for cooperation and offered support in contacting the local community and other residents who are interested in the past. This might be a first step to create a network of local enthusiasts of archaeology and history, who can provide assistance in community outreach activities.
The December visit to Soba was inspiring. It seems that among people living in the area, there are many who are open to cooperation. This refers to residents as well as local authorities. This situation shows that there is still a possibility to make limited studies in areas which are already overbuilt. Since more than the half of the site is now under modern buildings, this is worth considering. A dialogue with the local community about the future perspectives and possibilities of cooperation in research, protection and promotion of local histories should be initiated. For these kinds of studies and activities, an independent team, headed by a cultural anthropologist and including archaeologists and interpreters should be created.