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Figure 14. Mean site debris distribution with respect to water depth. The dashed line shows the trend of the data. HMS Chamois has been excluded due to lack of information. aaa i s ae Sub-bottom profiling systems have been used successfully in the study of ancient and historical shipwrecks [31,40,41] but have proved to be of limited use when surveying WWI, WWII and modern shipwrecks. On the other hand, those acoustic systems offer important information regarding the modifications of the sediment regimes due to the existence of the shipwreck. In this paper, sub-bottom profilers present valuable data concerning the erosion and the slight deformation of the sediments at the close vicinity of the shipwrecks. Furthermore, those systems together with side scan sonar systems suggest the formation of small crater-like features around the shipwrecks due to their loading on gas charged sediments and consequently the gas seepage. en ee 2 a ay -- -—. ¢ te + ¥ uae i =e sy = ig dag wae

Figure 14 Mean site debris distribution with respect to water depth. The dashed line shows the trend of the data. HMS Chamois has been excluded due to lack of information. aaa i s ae Sub-bottom profiling systems have been used successfully in the study of ancient and historical shipwrecks [31,40,41] but have proved to be of limited use when surveying WWI, WWII and modern shipwrecks. On the other hand, those acoustic systems offer important information regarding the modifications of the sediment regimes due to the existence of the shipwreck. In this paper, sub-bottom profilers present valuable data concerning the erosion and the slight deformation of the sediments at the close vicinity of the shipwrecks. Furthermore, those systems together with side scan sonar systems suggest the formation of small crater-like features around the shipwrecks due to their loading on gas charged sediments and consequently the gas seepage. en ee 2 a ay -- -—. ¢ te + ¥ uae i =e sy = ig dag wae

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Figure 1. Region of interest (ROI). The red circles indicate the approximate position of the wrecks. The black circles indicate the wrecks surveyed by the Laboratory of Marine Geology and Physical (LMGPO). Each number on the map corresponds to the serial number of a wreck that appears in the list of Table 1. The inset picture shows the location of the ROI in Greece. Figure 1. Region of interest (ROI). The red circles indicate the approximate position of the wrecks. The black circles indicate the wrecks surveyed by the Laboratory of Marine Geology and Physical (LMGPO).
Figure 1. Region of interest (ROI). The red circles indicate the approximate position of the wrecks. The black circles indicate the wrecks surveyed by the Laboratory of Marine Geology and Physical (LMGPO). Each number on the map corresponds to the serial number of a wreck that appears in the list of Table 1. The inset picture shows the location of the ROI in Greece. Figure 1. Region of interest (ROI). The red circles indicate the approximate position of the wrecks. The black circles indicate the wrecks surveyed by the Laboratory of Marine Geology and Physical (LMGPO).
Table 1. List of wrecks present in the ROI. The wrecks that have been surveyed by LMGPO appear in bold letters. The symbol ~ next to depth values denote uncertainty with respect to the actual value. N/K stands for not known. N/A stands for not applicable. SSS stands for side scan sonar, SBP stands for sub-botton profiler, MBES stands for multi-beam echo-sounder and GT stands for ground truthing.
Table 1. List of wrecks present in the ROI. The wrecks that have been surveyed by LMGPO appear in bold letters. The symbol ~ next to depth values denote uncertainty with respect to the actual value. N/K stands for not known. N/A stands for not applicable. SSS stands for side scan sonar, SBP stands for sub-botton profiler, MBES stands for multi-beam echo-sounder and GT stands for ground truthing.
Figure 2. “Fiskardo” shipwreck (modified by [30,31]). (a) High resolution side scan sonar image showing the general shipwreck site (1: ancient shipwreck, 2: sedimentary seafloor substrates, 3: rocky substrates with elevation and microrelief, 4: target of unknown origin, 5: anchoring marks); (b) and (c) different views of side scan sonar images of the “Fiskardo” shipwreck and her amphorae lying on a muddy sand seafloor; (d) a chirp sub-bottom seismic profile along the longitudinal axis of the amphorae cargo. The arrows indicate the side limits of the cargo and the dashed white line the probable hull bottom. The hard substrate and the surficial sedimentary cover (SC) are also shown; and (e) the bathymetry of the wreck site by MBES. the general shipwreck site (1: ancient shipwreck, 2: sedimentary seafloor substrates, 3: rocky substrates
Figure 2. “Fiskardo” shipwreck (modified by [30,31]). (a) High resolution side scan sonar image showing the general shipwreck site (1: ancient shipwreck, 2: sedimentary seafloor substrates, 3: rocky substrates with elevation and microrelief, 4: target of unknown origin, 5: anchoring marks); (b) and (c) different views of side scan sonar images of the “Fiskardo” shipwreck and her amphorae lying on a muddy sand seafloor; (d) a chirp sub-bottom seismic profile along the longitudinal axis of the amphorae cargo. The arrows indicate the side limits of the cargo and the dashed white line the probable hull bottom. The hard substrate and the surficial sedimentary cover (SC) are also shown; and (e) the bathymetry of the wreck site by MBES. the general shipwreck site (1: ancient shipwreck, 2: sedimentary seafloor substrates, 3: rocky substrates
Figure 3. SS Ardena shipwreck as depicted (a) and (b) by the side scan sonar (db: wreck debris, red lines show the debris field) and (c) by the sub-bottom profiler (insets: the dotted red line shows the seabed depression).
Figure 3. SS Ardena shipwreck as depicted (a) and (b) by the side scan sonar (db: wreck debris, red lines show the debris field) and (c) by the sub-bottom profiler (insets: the dotted red line shows the seabed depression).
Figure 4. HMS Perseus. (a—e) side scan sonar images (targets are shown inside red circles), the acoustic shadow of the wreck presents the sail in detail; (f) bathymetry from multi-beam echo-sounder; (g-i), high resolution seismic profiles showing the wreck (hyperbolic echoes) resting on loose sandy sediments. Figure 4. HMS Perseus. (a—e) side scan sonar images (targets are shown inside red circles), the acoustic
Figure 4. HMS Perseus. (a—e) side scan sonar images (targets are shown inside red circles), the acoustic shadow of the wreck presents the sail in detail; (f) bathymetry from multi-beam echo-sounder; (g-i), high resolution seismic profiles showing the wreck (hyperbolic echoes) resting on loose sandy sediments. Figure 4. HMS Perseus. (a—e) side scan sonar images (targets are shown inside red circles), the acoustic
Figure 5. (a) SS Mars shipwreck as depicted by the side scan sonar (db: wreck debris); (b,c) comparison of the silhouette of the ship based on acoustic shadow in the side scan sonar record and a historic photo.
Figure 5. (a) SS Mars shipwreck as depicted by the side scan sonar (db: wreck debris); (b,c) comparison of the silhouette of the ship based on acoustic shadow in the side scan sonar record and a historic photo.
Figure 6a,b show two side scan sonar images acquired at different frequencies (100 and 500 kHz) of the Kapros wreck. The piles of artillery missiles are scattered in an area of approximately 15 x 4 m. The debris field is small and very few artifacts are scattered within 6 m around the wreck. The bathymetry of the wreck site appears in Figure 6c. The wreck is also barely detectable on the seismic profile as indicated by the overlapping hyperbolic echoes almost tangent to the seafloor (Figure 6d). The wreck lies on the seafloor which consists of a thick (at least 15 m) sequence of soft stratified sediments (Figure 6d). The debris field is small and very few artifacts are scattered within 6 m around the wreck. The bathymetry 4.6. SS Svein Jarl
Figure 6a,b show two side scan sonar images acquired at different frequencies (100 and 500 kHz) of the Kapros wreck. The piles of artillery missiles are scattered in an area of approximately 15 x 4 m. The debris field is small and very few artifacts are scattered within 6 m around the wreck. The bathymetry of the wreck site appears in Figure 6c. The wreck is also barely detectable on the seismic profile as indicated by the overlapping hyperbolic echoes almost tangent to the seafloor (Figure 6d). The wreck lies on the seafloor which consists of a thick (at least 15 m) sequence of soft stratified sediments (Figure 6d). The debris field is small and very few artifacts are scattered within 6 m around the wreck. The bathymetry 4.6. SS Svein Jarl
The survey of Svein Jarl from LMGPO was performed about 25 years ago when only analogue side scan sonar records could be produced. Thus, the side scan images in Figure 7a,b are not of good quality. Nevertheless, when comparing the side scan images to actual photos of the ship (Figure 7c,d) it is obvious that the side scan images adequately capture the main SS Svein Jarl’s features such as: (1) the bow and (2) the funnel in Figure 7a; (1) the keel, (2) the propellers, (3) the massive damage on the bow in Figure 7b. In Figure 7b, (4) the acoustic shadow and (5) the towfish trackline also appear.
The survey of Svein Jarl from LMGPO was performed about 25 years ago when only analogue side scan sonar records could be produced. Thus, the side scan images in Figure 7a,b are not of good quality. Nevertheless, when comparing the side scan images to actual photos of the ship (Figure 7c,d) it is obvious that the side scan images adequately capture the main SS Svein Jarl’s features such as: (1) the bow and (2) the funnel in Figure 7a; (1) the keel, (2) the propellers, (3) the massive damage on the bow in Figure 7b. In Figure 7b, (4) the acoustic shadow and (5) the towfish trackline also appear.
y Figure 8. “Pump house” shipwreck. (a) Regional 100 kHz sonograph showing the “Pump house’ wreck and its environment (db: wreck debris, dp: seabed depressions); (b) 500 kHz sonograph showing the main structural components of the “Pump house” wreck (1: vertical bow, 2: stern, 3: propellers, 4: bridge and 5: heavy damage on the bow); (c) the mast of the wreck; (d) seismic profile showing the “pump-wreck” and the slightly deformed seafloor sediments around the wreck. Enhanced reflectors are visible about 4 m below the seafloor; and (e) the bathymetry of the wreck site. The interpretation of the acoustic data collected from the “pump house” wreck and the visual inspection in combination with the available shipwreck data of Patras Gulf do not permit clear identification of the wreck. The “Pump house” wreck could be the steamboat merchant “Christoforos”. “Christoforos” was a cargo ship built on 1889 at Liibeck shipyards (Germany) as Kollund and then was renamed to Alide. She sunk on the 1st of February 1921 in heavy weather.
y Figure 8. “Pump house” shipwreck. (a) Regional 100 kHz sonograph showing the “Pump house’ wreck and its environment (db: wreck debris, dp: seabed depressions); (b) 500 kHz sonograph showing the main structural components of the “Pump house” wreck (1: vertical bow, 2: stern, 3: propellers, 4: bridge and 5: heavy damage on the bow); (c) the mast of the wreck; (d) seismic profile showing the “pump-wreck” and the slightly deformed seafloor sediments around the wreck. Enhanced reflectors are visible about 4 m below the seafloor; and (e) the bathymetry of the wreck site. The interpretation of the acoustic data collected from the “pump house” wreck and the visual inspection in combination with the available shipwreck data of Patras Gulf do not permit clear identification of the wreck. The “Pump house” wreck could be the steamboat merchant “Christoforos”. “Christoforos” was a cargo ship built on 1889 at Liibeck shipyards (Germany) as Kollund and then was renamed to Alide. She sunk on the 1st of February 1921 in heavy weather.
Figure 9. “Old Iron” shipwreck. (a) Sonograph showing the “Old Iron” wreck (1: bow, 2: stern, 3: superstructure, 4: crack of the hull, df: debris filed, rp: rope, pm: pockmarks); (b) 3.5 kHz profile (eh: enhanced reflectors, vd: acoustic void area); and (c) the bathymetry of the wreck site by MBES. In the same marine survey that the “Pump house” wreck (Section 4.7) was investigated the presence of one more wreck was revealed: the “Old Iron” wreck. The wreck lies at an average water depth of 41 m and is oriented in a northeast-southwest direction. The length of the wreck as measured from the MBES bathymetry is 31 m and her width is 11 m. A rope tied to the damaged stern is clearly visible on the sonograph (Figure 9a). The relative position of the acoustic shadow of the rope cast by the sonar indicates that the rope is slightly floating above the seabed. A debris field densely distributed around the damaged stern has been recorded on the sonograph; it is indicated by the large number of small-size high reflectivity objects (Figure 9a).
Figure 9. “Old Iron” shipwreck. (a) Sonograph showing the “Old Iron” wreck (1: bow, 2: stern, 3: superstructure, 4: crack of the hull, df: debris filed, rp: rope, pm: pockmarks); (b) 3.5 kHz profile (eh: enhanced reflectors, vd: acoustic void area); and (c) the bathymetry of the wreck site by MBES. In the same marine survey that the “Pump house” wreck (Section 4.7) was investigated the presence of one more wreck was revealed: the “Old Iron” wreck. The wreck lies at an average water depth of 41 m and is oriented in a northeast-southwest direction. The length of the wreck as measured from the MBES bathymetry is 31 m and her width is 11 m. A rope tied to the damaged stern is clearly visible on the sonograph (Figure 9a). The relative position of the acoustic shadow of the rope cast by the sonar indicates that the rope is slightly floating above the seabed. A debris field densely distributed around the damaged stern has been recorded on the sonograph; it is indicated by the large number of small-size high reflectivity objects (Figure 9a).
Figure 10. MV Ag. Nektarios shipwreck as depicted by the side scan sonar (db: wreck debris).
Figure 10. MV Ag. Nektarios shipwreck as depicted by the side scan sonar (db: wreck debris).
Figure 11. (a,b) MV Carinthia shipwreck as depicted by the side scan sonar; and (c) a photo of the ship [37].
Figure 11. (a,b) MV Carinthia shipwreck as depicted by the side scan sonar; and (c) a photo of the ship [37].
Figure 12. HMS Chamois shipwreck (a) as depicted by the side scan sonar (1: acoustic shadow, 2: elongated features, 3: scour, 4: mast); and (b) in a photograph. FECeGea alld UWle stlip DEsall tO sus WIT Le Sterr) Ur It Ulsdppedread DELOW Ule SuTTaCe OF ULE Sed. Figure 12a is a side scan sonar image of the shipwreck. The side scan sonar survey took place approximately 15 years ago so the image is of poor quality but two points are worth mentioning: (a) the silhouette of the wreck in the side scan image corresponds nicely to the actual ship (Figure 12b) and (b) there is an interesting geomor phological feature related to t he wreck. In side scan sonar record, the wreck structure is characterized by high-backscatter returns followed by a well-developed acoustic shadow representing the silhouette of the shipwreck. A scour ex the wreck in an almost E-W (80/260° The scour is characterized by higher reflectivity (dark tone) com sediments. High reflectivity elonga orientation, tapering out ap ted features were also detec tending from the starboard side of proximately 150 m from the wreck pared to the surrounding seafloor ted running almost parallel to the scour and highlighting the dynamic characteristics of the shipwreck site. The current induced scour which has been formed almost perpendicular to the long-axis of the wreck, is in accordance with the prevailing currents in the area [38].
Figure 12. HMS Chamois shipwreck (a) as depicted by the side scan sonar (1: acoustic shadow, 2: elongated features, 3: scour, 4: mast); and (b) in a photograph. FECeGea alld UWle stlip DEsall tO sus WIT Le Sterr) Ur It Ulsdppedread DELOW Ule SuTTaCe OF ULE Sed. Figure 12a is a side scan sonar image of the shipwreck. The side scan sonar survey took place approximately 15 years ago so the image is of poor quality but two points are worth mentioning: (a) the silhouette of the wreck in the side scan image corresponds nicely to the actual ship (Figure 12b) and (b) there is an interesting geomor phological feature related to t he wreck. In side scan sonar record, the wreck structure is characterized by high-backscatter returns followed by a well-developed acoustic shadow representing the silhouette of the shipwreck. A scour ex the wreck in an almost E-W (80/260° The scour is characterized by higher reflectivity (dark tone) com sediments. High reflectivity elonga orientation, tapering out ap ted features were also detec tending from the starboard side of proximately 150 m from the wreck pared to the surrounding seafloor ted running almost parallel to the scour and highlighting the dynamic characteristics of the shipwreck site. The current induced scour which has been formed almost perpendicular to the long-axis of the wreck, is in accordance with the prevailing currents in the area [38].
Time periods of wrecks in inner lonian Sea Figure 13. Time periods of wrecks in inner Ionian Sea. Each blue colored bar indicates the total number of wrecks per time period while each orange colored bar indicates the number of wrecks surveyed by LMGPO per time period. WIECKS ITOIL LAQ0O~1LIOZ. The wrecks surveyed by LMGPO include one submarine and 10 ships. The ships are of various types: one cargo ship, one small boat, one tugboat, one leisure yacht and one destroyer. Each of these shipwrecks has some significance. “Fiskardo” is one of the four largest merchant shipwrecks from the st century AC-1st century AD period that have been found in the Mediterranean to date. SS Ardena has historical value as it serves as a reminder of the horrible fate of the Italian Acqui division. HMS Perseus’ story is related to one of the rare cases when a passenger managed to successfully escape a sunken submarine using the Davis apparatus. SS Mars and SS Svein Jarl were postwar victims of the minefields constructed during WWII. Kapros wreck adds useful historical information on the type of ammunitions and medical supplies used during WWII. “Pump house” wreck and “Old Iron” sites have interesting crater-like features. The “Old Iron” wreck site is extremely important from an environmental point of view, as the pockmarks formation surrounding it is probably due to the loading of the wreck on the seafloor soft sediments that led to fluid discharge. MVAgios Nektarios has the most extensive debris field and MV Carinthia was one of the most pioneering leisure yachts built in her era. Finally, HMS Chamois wreck site has interesting scour formations that have been formed due to the wreck. The preservation state of each shipwreck is controlled by three dominant environmental factors, i) physical controls, (ii) biological controls and (iii) chemical/pollution controls [24]. This paper focuses only on the physical controls on the shipwrecks as they emerged by the interpretation of a variety of marine sensing data; side scan sonar, multi-beam echo-sounding and sub-bottom profiling data. Nith the use of side scan sonar and multi-beam echo-sounder, large areas of seafloor can be surveyed rapidly, and water turbidity, currents, adverse environmental conditions and shipping traffic can little iffect these acoustic remote sensing methods. SSS mainly and MBES secondarily are very effective ‘ools for detecting objects/anomalies on the seafloor which can be considered as potential shipwrecks. Historic, WWI, WWII and modern shipwrecks can be easily detected and recognized even by a large
Time periods of wrecks in inner lonian Sea Figure 13. Time periods of wrecks in inner Ionian Sea. Each blue colored bar indicates the total number of wrecks per time period while each orange colored bar indicates the number of wrecks surveyed by LMGPO per time period. WIECKS ITOIL LAQ0O~1LIOZ. The wrecks surveyed by LMGPO include one submarine and 10 ships. The ships are of various types: one cargo ship, one small boat, one tugboat, one leisure yacht and one destroyer. Each of these shipwrecks has some significance. “Fiskardo” is one of the four largest merchant shipwrecks from the st century AC-1st century AD period that have been found in the Mediterranean to date. SS Ardena has historical value as it serves as a reminder of the horrible fate of the Italian Acqui division. HMS Perseus’ story is related to one of the rare cases when a passenger managed to successfully escape a sunken submarine using the Davis apparatus. SS Mars and SS Svein Jarl were postwar victims of the minefields constructed during WWII. Kapros wreck adds useful historical information on the type of ammunitions and medical supplies used during WWII. “Pump house” wreck and “Old Iron” sites have interesting crater-like features. The “Old Iron” wreck site is extremely important from an environmental point of view, as the pockmarks formation surrounding it is probably due to the loading of the wreck on the seafloor soft sediments that led to fluid discharge. MVAgios Nektarios has the most extensive debris field and MV Carinthia was one of the most pioneering leisure yachts built in her era. Finally, HMS Chamois wreck site has interesting scour formations that have been formed due to the wreck. The preservation state of each shipwreck is controlled by three dominant environmental factors, i) physical controls, (ii) biological controls and (iii) chemical/pollution controls [24]. This paper focuses only on the physical controls on the shipwrecks as they emerged by the interpretation of a variety of marine sensing data; side scan sonar, multi-beam echo-sounding and sub-bottom profiling data. Nith the use of side scan sonar and multi-beam echo-sounder, large areas of seafloor can be surveyed rapidly, and water turbidity, currents, adverse environmental conditions and shipping traffic can little iffect these acoustic remote sensing methods. SSS mainly and MBES secondarily are very effective ‘ools for detecting objects/anomalies on the seafloor which can be considered as potential shipwrecks. Historic, WWI, WWII and modern shipwrecks can be easily detected and recognized even by a large
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