Kiril Velkovsky

The aerial imagery has a long tradition of use as a surveying method in underwater archaeology. With the recent development of new technologies, its application has become more versatile and more common. This article will present the use of aerial photogrammetry in the archaeological survey of the submerged heritage of Nessebar, ancient Mesambria, on the Bulgarian Black Sea coast. A major application is the generation of a digital bathymetric model (DBM) of the seafloor, which is reliable and accurate approximately up to-3 m depth. It is especially useful in shallow waters and in the intertidal zone, where the implementation of multibeam echosounder scanning is not possible. The combined bathymetric data from multibeam echosounder and unmanned aerial vehicles (UAVs) are base for generating a precise and accurate surface model of the Nessebar peninsula and its adjacent aquatory with satisfactory resolution (25 cm raster for the seafloor) up to-18 m depth. Another major application is the production of orthophotomosaic (OM) with high resolution (5 cm raster). Both techniques have been used for the creation of a multilayer GIS database, documentation and mapping of the archaeological structures and their environment, surveying for unknown archaeological sites, virtual reconstruction of the paleolandscape and its evolution. An important advantage of aerial photogrammetry is its economic application, fast and logistically easy field data acquisition, relatively fast data processing and low-budget equipment.

The article presents some case studies of the negative impact of human activities on underwater cultural heritage from the Black Sea. A serious problem is pollution and litter disposal in the historical harbours. The resulting conditions often endanger some impressive and well-preserved underwater cultural heritage sites. An advanced methodology for litter registering and assessment was developed and applied using remote sensing with side-scan sonar, subbottom profiler and orthophotography using a drone. The survey of deep-sea shipwrecks using remote operated vehicles (ROV's) discovered that some of them are almost covered with litter. The ancient remains act as traps which catch light litter objects (mostly items made of plastic), transported by the deep-sea currents. The litter seriously reduced the possibility for exploration and recording of some shipwrecks and their presentation to the public. The ROV and submarine surveys revealed the extent of the damage to numerous originally well-preserved shipwrecks as a result of the fishing industry practice of bottom trawling. All these cases of negative impact by human activities on the cultural heritage and its rapid deterioration raise the question of the necessity of prompt and adequate reactions and measures for the prevention of further damage to these endangered underwater archaeological monuments.

GEOPHYSICAL SURVEY ON THE ARCHAEOLOGICAL SITE „ANCIENT BONONIA“, KALETO QUARTER, VIDIN
Zdravko Dimitrov, Kiril Velkovski, Hristian Tsankov, Atanas Ivanov, Fionera Filipova, Ilko Tsvetkov
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The objectives of the study were to examine and confirm the presence of a fortification wall and tower N 9 from the Roman and Late Roman Bononia.
To accomplish the goals it was used a complex of two geophysical methods: Geo-radar (GPR) for areal monitoring with and geo-electrical tomography in 15 measurement profiles.
The paper presents in a brief from the results from the survey.

A magnetic survey covering 9510 sq. m (measurement density 1.0 x 0.2 m) was carried out on the western bank of the Durankulak Lake. The surveyed area extended from the newly built parking lot towards the touristic info center. The field data from caesium G-858 magnetometers (in vertical gradient mode) were additionally calibrated with reference to data from the magnetic observatory in Panagyurishte (PAG) and measurements of the magnetic susceptibility of two types of limestone abundant on the surface. The most promising results show a number of localized dipoles (possibly iron objects and/or fired installations), some rectangular correlations and several circular zones with low magnetic values. The latter could be compared to non-magnetic limestone accumulations with negative geometry (the so-called tholoi) known from the neighboring Hellenistic ritual area.

The goal of geophysical research in 2021 was a comprehensive study of the bottom of Durankulak Lake (Fig. 1). The following tools was employed: Side Scan Sonar 2 pcs. (StarFish 450H and StarFish 990) with visualization system for obtaining information about the nature of the lake bottom and the presence and / or absence of artificial objects; Compact sub bottom - SES 2000 Compact for bottom depth scanning and surface stratigraphy detection; and DGPS coordinating system with Heading (Trimble SPSx61) in Roll RTK configuration and geo-electrical resistance meter. Multibeam echosounder was also used to supplement the data.
      According to the tracing data, we were able to select only one layer of mud deposited on the strongly denuded rocks in Durankulak Lake. In places the muddy layer reaches a depth of over 4 m. The reason why the layers cannot be clearly traced in depth is the fact that the muddy bottom, due to the decomposition of deposited organic material, generates a constant swamp gas that shields the signal and limits the breakthrough capabilities of the equipment. In the environment of moving water masses, as is the case with the Black Sea bottom, this is not the case, but with the stagnant water of Durankulak Lake, this has become an insurmountable problem.
    In Durankulak Lake, 10 electric cross-sections were made, covering its entire area. The defined boundaries of the layers are stratified on the basis of specific resistances. The results confirmed the previous observations that the riverbed and flood terraces of the ancient river were formed by gravels, sands (mostly near the modern coastline), clay and precipitated loess. Of interest are the rise and fall of the strata registered in several of the profiles, which (unprovable for now) could be interpreted as indications of the presence of fault lines.
    Summarizing the results obtained from the research of Durankulak Lake and the adjacent Black Sea shelf, we draw a clear picture of the paleorelief of the area (Fig. 4). The contours of the ancient river, as well as the river pools areas, became very apparent. It was found that in some places the width of the ancient river reached 70–80 m. The greatest measured depth is in the eastern part of the lake – -4.25 m from elevation 0, the modern water mirror. Detailed bathymetry shows that the area around the Big and Small Islands has a slightly special relief. At about 50 m to the north, the bottom drops to -3.20 m. There is a large depression which can be interpreted as a river pool, a swampy area during the dry months of the year. Data have been found between the two islands for the presence of a pronounced rib connecting them, an indication of the existence in ancient times of a land connection between the Big and Small Islands. The established terrain configuration on the western bank of the ancient river showed that in ancient times the areas south and north of the Big Island were relatively flat and probably inhabited.
    Data from the side-scan sonar (Compact sub bottom) show that in front of the eastern cape of the Big Island there is a significant accumulation of stones. Scattered stones are also found on the eastern shore of the lake, opposite the Small Island. The sonar images also show the contours of a sunken boat, as well as those of several of the metal cylindrical girders of the pontoon once connecting the coast with the Small Island.

През лятото на 2014 г. при изкопни работи свързани със строителството на ЛОТ 2 от автомагистрала „Струма“, между километър 343+760 и километър 343+860, на около 1,8 km северно от с. Мурсалево и около 3 km югоизточно от с. Бобошево, са открити останките на антично селище (фиг. 1). От проведените в края на есента спасителни археологически разкопки става ясно, че се касае за римско селище от периода III – IV в. сл. Хр. Настъпващата зима и необходимостта от бързи действия, поради кратките срокове за проучване, свързани със строящата се магистрала, наложиха провеждането на геофизични проучвания, с помощта на които да бъде добита по-пълна представа за разположението и структурата на античното селище. Получената геофизична информация следва да спести време и средства, давайки насочваща информация за евентуалното разположение на неразкрити зидове, останки от сгради, пещи, артефакти и др. при бъдещите спасителни разкопки в неизследваните участъци от обекта.

In the summer of 2014 during excavation works related to the construction of the LOT 2 of the Struma highway were found the remains of an ancient settlement. The object is located between the km 343+740 and km 343+840, about 1,8 km north from Mursalevo village and about 3 km southeast from Boboshevo village. According to the conducted in late autumn archaeological rescue excavations was clarified that this was a Roman villa rustica dated IIIrd – IVth century AD. The coming winter and the need of rapid reaction due to the highway under construction forced the quick implementation of geophysical studies in order to clarify the situation in the undiscovered areas of the ancient settlement. The applied geophysical methods (geomagnetic and electrical) supported the future archaeological excavations with excellent results and guidance information about the location and the orientation of undiscovered underground walls, foundations and buildings' remains as well as overall information about the structure and the size of the settlement.

The attached paper is the resume to the presentation. Abstract: The application of geophysical prospecting methods for the purposes of underwater archaeological research allows for the delineation of areas of potential archaeological interest.
The present paper focuses on the results achieved during several research projects carried out by the Centre for Underwater Archaeology in 2014 in the aquatoria of Varna (Pasha dere), Pomorie,  Chernomorets and Sozopol in relation to the implementation of several investments projects, and in the southern bay of Kiten in relation to the survey and underwater archaeological excavation of an Early Bronze Age settlement funded by the Ministry of Culture.