The ancient site of Olympia is located on the northern fringe of the Basin of Makrisia at the confluence of the Kladeos and Alpheios rivers (western Peloponnese, Greece) and was used as a venue for the Panhellenic Games from Archaic times until the 4th century AD. Geophysical prospection (frequency domain electromagnetic induction and electrical resistivity tomography) was carried out as a basis for detailed geoarchaeological investigations. In doing so, we identified a previously unknown building structure adjacent to the Altis, the inner part of the sanctuary at Olympia. Situated south of the Southwest Thermae, this structure measures at least 100 m (WSW-ENE) by 80 m (NNW-SSE). Its external orientation is in line with the orientation of the Southwest Thermae and the Leonidaion. We retrieved sediment cores from 17 different locations in combination with high-resolution direct push sensing from inside the newly found structure. All cores revealed distinct units of organic-rich limnic sediments dominated by clay and fine silt. Geochemical and micropaleontological analyses of selected sediment samples indicate highly eutrophic conditions, as evidenced by elevated phosphorous concentrations and the dominance of the ostracod species Cyprideis torosa, which is able to live under low-oxygen conditions. Moreover, molecular biomarker analyses show a significant input of lipid fecal markers, implying strong anthropogenic pollution. Further, the limnic sediments include numerous charcoal remains and abundant diagnostic artifacts such as ceramic fragments and building material. Radiocarbon dating documents that these limnic conditions persisted within the building structure from at least the 5th century BC to the 6th century AD. The identified building structure lies in the immediate proximity to the Lake of Olympia, which was recently found to have existed from the mid-Holocene to the Medieval period. Its characteristic filling with fine-grained sediments and multiple indications for a strongly polluted and heavily used standing water environment let us hypothesize that it was possibly used as a harbor installation. A harbor at ancient Olympia could have been used to reach the sanctuary by boat and to transport goods of all kinds.

Along the southern North Sea coast from the Netherlands to Denmark, human cultivation efforts have created a unique cultural landscape. Since the Middle Ages, these interactions between humans and natural forces have induced major coastal changes. In North Frisia (Germany), storm floods in 1362 AD and 1634 AD turned wide areas of embanked cultural land into tidal flats. Systematic geoarchaeological investigations between Nordstrand and Hallig Südfall comprise coring, trenching, sedimentary, geochemical and microfaunal palaeoenvironmental parameter analyses and radiocarbon dating. Together with geophysical prospection results and archaeological surveys, they give insights into the landscape’s development and causes for land losses. Results reveal that fens and bogs dominated from c. 800 BC to 1000 AD but are mostly missing in the stratigraphy. Instead, we found 12th to 14th cent. AD settlement remains directly on top of a pre-800 BC fossil marsh. This hiatus of c. 2000 years combined with local ‘Hufen’ settlements implies an extensive removal of peat during cultivation eventually resulting in the use of underlying marshland for agricultural purposes. Fifteenth cent. AD tidal flat deposits on top of the cultivated marsh prove that human impact lowered the ground surface below the mean high water of that time, clearly increasing the coastal vulnerability. We consider these intensive human–environment interactions as a decisive trigger for the massive loss of land and establishment of the tidal flats in North Frisia that are currently part of the UNESCO World Heritage “Wadden Sea”.

This study examines the Roman burgus and medieval lowland castle ‘Zullestein’ near Biblis (Bergstraße district/Hessen/Germany) and its surrounding fluvio-scape. The aim of the study is to reassess the appearance of the fortifications and the surrounding area at the confluence of the River Weschnitz and the River Rhine based on the excavation results from the 1970s and current geoarchaeological research on site. Our approach encompasses electrical resistivity tomography, direct push sensing, sediment coring and the use of a high-resolution digital elevation model in combination with historical depictions of the Zullestein site from the 17th century AD. The findings of this integrative approach indicate that the Roman fort was likely located at a secondary channel of the River Rhine. With the renewed occupation of the Zullestein site by Lorsch Abbey during Carolingian times and the expansion into a lowland castle in the 11th century, the site was now located at the Weschnitz mouth into the Rhine, likely as part of anthropogenic interventions related to the Weschnitz fluvioscape. Traces of the final phase of the castle at the time of the Thirty Years’ War can still be seen in the terrain today and their attribution to individual elements of the historical account can be confirmed by the geoarchaeological results. The combination of methods presented in this study is a suitable option if excavations are not possible.

The UNESCO World Heritage Wadden Sea holds remains of a medieval cultural landscape shaped by interactions between man and natural forces. From the Netherlands to Denmark, human efforts of cultivating low-lying areas created a unique coastal landscape. Since the Middle Ages, storm floods widely drowned embanked cultural land and especially affected North Frisia (Germany), where once fertile marshland was permanently turned into tidal flats. One key region, the Edomsharde, was widely destroyed in 1362 AD. Medieval settlement remains still occur in the tidal flats around the island Hallig Südfall and are commonly associated with Edomsharde’s trading centre Rungholt—ever since a symbol for the region’s drowned landscapes and focus of this study. We present a first-time comprehensive reconstruction of this medieval settlement by means of new geophysical, geoarchaeological and archaeological data. Our results reveal remains of up to 64 newly found and rectified dwelling mounds, abundant drainage ditches, a seadike, and especially the discovery of Edomshardes’s main church as important landmark in this former cultural landscape. These finds together with the documented imported goods confirm a thriving society, involved in transregional trade and thereby close a significant gap in medieval history not only for North Frisia, but the entire Wadden Sea region.

Intensive human intervention in the natural drainage system of the Hessische Ried (Upper Rhine Graben, Germany) resulted in the transformation of a large wetland into an intensively used cultural landscape. At least since the first century CE, when Romans conducted early river regulation and water management, the natural water network has experienced extensive anthropogenic re-organisation. The LandGraben project focuses on the reconstruction of the natural and anthropogenic watercourse systems along the river Landgraben, a tributary to the river Rhine in the northern Hessische Ried. Several rivers from the southern Hessische Ried could have fed the river Landgraben during Roman times via the meandering Palaeo-Neckar depression, thus increasing both length and discharge of the Roman waterway.In this study, we present results of our investigations within the southern Hessische Ried to reconstruct the former channel network that was used by Romans for the transportation of troops, wares and border security. Our approach integrates the use of high-resolution digital elevation models (DEMs) as a base for geophysical measurements (electrical resistivity tomography, ERT), direct push sensing and sediment coring in combination with sedimentological and geochemical analyses of the encountered sedimentary units. Local chronostratigraphies were established based on radiocarbon dating.Based on our results, we are able to differentiate a palimpsest of several abandoned fluvial channels throughout the southern Hessische Ried and to reconstruct the spatio-temporal development of the corresponding fluvial systems. Chronostratigraphic data show that the Palaeo-Neckar stopped flowing through the Hessische Ried around 10 000 cal BCE. Moreover, we found that the river Weschnitz, the largest of the possible Landgraben tributaries, stopped flowing through the Palaeo-Neckar depression at ca. 3000 cal BCE. Instead, it took a right-angled shortcut westwards to the river Rhine, north of the city of Lorsch. For the first time, we present geomorphological evidence that the river Weschnitz was not diverted by the Romans as speculated so far. This is corroborated by numerous wooden posts of human-made construction crossing an E-W running water course at the modern Weschnitz knee, with the oldest posts being dendrochronologically dated to the fourth and third millennia BCE. We further argue that the river Winkelbach/Lauter formed its knee towards the river Rhine and thus left the Palaeo-Neckar depression not later than the second century CE but most probably even contemporaneously with the formation of the Weschnitz diversion. In the case of the Winkelbach/Lauter, a high-energy flood event presumably related to strong rainfall and/or meltwater processes in the Odenwald Mountains is assumed to be responsible for the initiation of the new, diverted water course. With regard to the Landgraben and its use as a waterway within the Roman fluvioscape of the Hessische Ried, we therefore conclude that the Romans successfully collected water from several smaller rivers, such as from the rivers Modau and Darmbach and from even smaller tributaries, to make the river Landgraben a navigable waterway. The rivers Weschnitz and Winkelbach/Lauter, however, did not contribute any water to the Landgraben system during Roman times. Umfangreiche menschliche Eingriffe in das natü rliche Entwä sserungssystem des Hessischen Rieds (Oberrheingraben, Deutschland) fü hrten zur Umwandlung eines weiträ umigen Feuchtgebiets in eine intensiv genutzte Kulturlandschaft. Spä testens seit dem 1. Jahrhundert n. Chr., als die Rö mer Regulierungsma ss nahmen an Flü ssen ergriffen, wurde das natü rliche Gewä ssernetz tiefgrü ndig umgestaltet. Das LandGraben-Projekt befasst sich mit der Rekonstruktion der natü rlichen und anthropogenen Gewä sserstrukturen entlang des Landgrabens, einem Nebenfluss des Rheins im nö rdlichen Hessischen Ried. Mehrere Flü sse aus dem sü dlichen Hessischen Ried kö nnten den Landgraben wä hrend der Rö merzeit ü ber die Altneckarniederung gespeist haben und damit sowohl die Lä nge als auch den Abfluss der rö mischen Wasserstra ss e vergröss ert haben.Diese Studie stellt die Rekonstruktion des ehemaligen Flussnetzes vor, das von den Rö mern fü r den Transport von Truppen, Waren und zur Grenzsicherung genutzt wurde. Unser Ansatz kombiniert hochauflö sende digitale Gelä ndemodelle, geophysikalische Messungen (Geoelektrische Widerstandstomographie), Direct Push Sensing und Sedimentkernbohrungen in Verbindung mit sedimentologischen und geochemischen Analysen der vorliegenden Sedimenteinheiten. Lokale Chronostratigraphien wurden auf der Grundlage von Radiokohlenstoffdatierungen erstellt.Basierend auf unseren Ergebnissen konnte zwischen verschiedenen verlandeten Flussrinnen im sü dlichen Hessischen Ried differenziert und die raum-zeitliche Entwicklung der entsprechenden fluvialen Systeme rekonstruiert werden. Chronostratigraphische Daten zeigen, dass der Altneckar um ca. 10 000 v. Chr. aufhö rte, durch das Hessische Ried zu entwä ssern. Bereits um ca. 3000 v. Chr. verlie ss die Weschnitz, der gröss te der mö glichen Landgrabenzuflü sse, die Altneckar-Niederung. Stattdessen nahm sie nö rdlich von Lorsch eine rechtwinklige Abkü rzung westwä rts zum Rhein. Damit ist erstmals geomorphologisch nachgewiesen, dass die Weschnitz nicht, wie bisher vermutet, von den Rö mern umgeleitet wurde. Diese Annahme wird durch das Vorhandensein zahlreicher Holzpfä hle unterstü tzt, die der Ü berquerung eines in Ost-West Richtung verlaufenden Flie ss gewä ssers am heutigen Weschnitzknie dienten. Fü r die ä ltesten dieser Pfä hle liegen dendrochronologische Datierungen in das 4. und 3. Jahrtausend v. Chr. vor. Weiterhin konnte festgestellt werden, dass der Winkelbach bzw. die Lauter die Altneckar-Niederung jedenfalls vor dem 2. Jh. n. Chr. in Richtung Rhein verlassen hat und sein Knie bildete. Hö chstwahrscheinlich geschah dies wesentlich frü her, nä mlich gleichzeitig mit der Entstehung des Weschnitzknies. Im Falle der Laufä nderung von Winkelbach bzw. Lauter wird ein hochenergetisches Ü berflutungsereignis, vermutlich im Zusammenhang mit starken Niederschlä gen und/oder Schmelzwasserprozessen im Odenwald verantwortlich gemacht. Im Hinblick auf den Landgraben und seine Nutzung als Wasserstra ss e in der rö mischen Flusslandschaft des Hessischen Rieds lä sst sich festhalten, dass die Rö mer das Wasser mehrerer kleinerer Flü sse, unter anderem der Modau, des Darmbachs sowie weiterer kleinerer Nebenflü sse, sammelten, um den Landgraben schiffbar zu machen. Die Flü sse Weschnitz und Winkelbach bzw. Lauter hingegen fü hrten dem Landgrabensystem in rö mischer Zeit kein Wasser zu.

The Storegga slide tsunami (SST) at ca. 8100 ± 100–250 cal BP is known to be the largest tsunami that affected the North Sea during the entire Holocene. Geological traces of tsunami landfall were discovered along the coasts of Norway, Scotland, England, Denmark, the Faroes and Shetland Islands. So far, the German North Sea coast has been considered as being well protected due to the wide continental shelf and predominant shallow water depths, both assumed to dissipate tsunami wave energy significantly, thus hindering SST propagation dynamics. The objective of our research was to clarify if the SST reached the German Bight and if corresponding sediment markers can be found. Our research was based on the in-depth investigation of a 5 m long section of the research core Garding-2 from Eiderstedt Peninsula near Garding in North Frisia known from a previous study. For this, we newly recovered sediment core Garding-2A at exactly the same coring location as core Garding-2. Additionally, high-resolution Direct Push sensing data were collected to gain undisturbed stratigraphic information. Multi-proxy analyses of sediment material (grain size, geochemical, geochronological and microfaunal data) were carried out to reconstruct palaeoenvironmental and palaeogeographical conditions. We identified a high-energy event layer with sedimentological (e.g., erosional unconformity, rip-up clasts, fining-upward), microfaunal (e.g., strongly mixed foraminiferal assemblage) and other features typical of tsunami influence and identical in age with the SST, dated to ca. 8.15 ka cal BP. The event layer was deposited at or maximum ca. 1–1.5 m below the local contemporary relative sea level and several tens of kilometers inland from the coastline within the palaeo-Eider estuarine system beyond the reach of storm surges. Tsunami facies and geochronological data correspond well with SST signatures identified on the nearby island of Rømø. SST candidate deposits identified at Garding represent the southernmost indications of this event in the southeastern North Sea. They give evidence, for the first time, of high-energy tsunami landfall along the German North Sea coast and tsunami impact related to the Storegga slide. SST deposits seem to have been subsequently reworked and redeposited over centuries until the site was affected by the Holocene marine transgression around 7 ka cal BP (7.3–6.5 ka cal BP). Moreover, the transgression initiated energetically and ecologically stable shallow marine conditions within an Eider-related tidal channel, lasting several millennia. It is suggested that the SST was not essentially weakened across the shallow continental shelf of the North Sea, but rather caused tsunami run-up of several meters (Rømø Island) or largely intruded estuarine systems tens of kilometers inland (North Frisia, this study). We, therefore, assume that the southern North Sea coast was generally affected by the SST but sedimentary signals have not yet been identified or have been misinterpreted. Our findings suggest that the German North Sea coast is not protected from tsunami events, as assumed so far, but that tsunamis are also a phenomenon in this region.

Corfu Island is the northernmost of the Ionian Islands located in the eastern Mediterranean Sea. As a result of the collision of the African and the Eurasian plates, the island lies within an area of exceptional tectonic stress with all types of plate boundaries in its proximity. In the Adriatic Sea north of Corfu, the Adriatic microplate collides with the Eurasian plate and to its south, in the Ionian Sea, the African oceanic plate is being subducted beneath the Aegean microplate forming the Hellenic Arc. Earthquakes and co-seismic crustal movement which can cause extreme wave events have been recorded for the area. This paper presents geomorphological, sedimentary and microfaunal evidence of repeated tsunami landfalls in the Alykes coastal lagoon at the southwestern coast of Corfu Island. Using the radiocarbon dating approach, the beginning of the lagoon was dated back to at least the 6 th millennium BC. Siltation of the lagoon was repeatedly interrupted by high-energy tsunami impacts. The two most prominent tsunami traces were found for the time immediately before 5.7 ka cal BC and the time between 5.2-5.0 ka cal BC. The ages of the tsunami events correspond well with local, regional, and supra -regional tsunami signatures found along the northwest and the west coasts of Greece. Subordinate traces for younger extreme wave events known to have affected the Gulf of Corfu are also indicated in the Alykes palaeotsunami archive and are likely related to co-seismic movements of the southern part of Corfu Island in the 4 th century BC. The results contribute to the understanding of the environmental effects of palaeotsunami impacts and underline a strongly non-uniform neotectonic behaviour of Corfu Island as a whole.

Historical documents and maps as well as diverse archaeological findings in the Wadden Sea off Nordstrand Peninsula in North Frisia (Germany) suggest a formerly settled landscape in medieval times and severe changes of the coastline since then. Based on historical maps, the area of the original Trendermarsch polder (Nordstrand) is considered, to have been much larger in the High Middle Ages than it is today. Overall, the pre-medieval land has been settled and cultivated since medieval times when extensive cultivation shaped the landscape. As typical of the region, storm surges had a powerful impact on the embanked land and led to severe changes of the medieval coastline by dyke breaches and land losses. Consequently, for the medieval Trendermarsch, it is assumed that there are archaeological remains from this time period preserved in the Wadden Sea beneath the recent tidal flat sediments. Geophysical and geoarchaeological investigations such as sedimentary, geochemical and microfaunal analyses of a sediment core were carried out in the tidal flats of the Trendermarsch to search for medieval settlement patterns and to reconstruct its development. Radiocarbon dating and historical reports were used to provide a basic chronological timeframe. Our results revealed traces of a medieval Trendermarsch settlement directly in front of today's sea dyke off Nordstrand Peninsula as part of a larger settlement area. To sum up, we found, for the first time, geoarchaeological evidence that the area of the present Wadden Sea off Nordstrand Peninsula hides various traces of the sunken medieval Trendermarsch. Yet, the study area is subject to ongoing transformation due to erosion and sediment accumulation, in relation to tides and storm events.

The Romans carried out early river regulation and water management in the Hessische Ried already in the 1 st century AD. Roman waterways enabled the transportation of troops and material and were of strategic importance to secure the territory of the Roman Empire. Small fortlets, so called burgi (singular burgus), were constructed along the tributaries of the River Rhine in late Roman times. The burgus at Trebur-Astheim represents such a Roman military site along the so-called Rhein -Limes. Its construction is dated to AD 364/375 by a Roman coin and the shape of its construction (Heising 2012) and was obviously part of the building program realized during the reign of the Emperor Valentinian I (AD 364-375). The archaeological site is located at the Schwarzbach/ Landgraben watercourse only a few kilometers southwest from its actual mouth into the River Rhine. This watercourse connects the western fringe of the Odenwald with the city of Mogontiacum/Mainz. To study this structure, a multi -method geophysical prospection was carried out at the burgus at Trebur-Astheim. We were able to trace the ground plan of the late Roman burgus first published by Heising (2012) showing a rectangle building at the center with a wing wall to both the northern and the southern side running towards the present riverbank. On this base, detailed geomorphological and geoarchaeological studies were carried out to clarify how the burgus was connected to the watercourse of the Schwarzbach/Landgraben, to collect information on the structure and function of the building and to establish a local geochronology. Our results show that the burgus was constructed at the very edge of the Lower Terrace directly facing the watercourse. The Lower Terrace edge has its westernmost position right in between the northern and southern wing wall of the burgus forming kind of a protruding nose. In front of the burgus, a semi -enclosed artificial basin was detected. Sediments prove that the burgus must have been open towards the fluvial system and that the burgus was not enclosed by a wall from the western side. Based on stratigraphic data, the protruding nose -type Lower Terrace section in between the wing walls was modelled as ramp into the burgus basin to pull vessels on the artificial river bank. The minimum water depth was reconstructed to be 0.7 m in front of the burgus. This and the overall geographic situation let us assume that the building was located at the Schwarzbach/Landgraben channel by the time of its use and not at the River Rhine itself. This assumption is in accordance with evidence of Roman -built canal sections of the Landgraben further upstream (Hanel 1995; Becker 2019). In our study area, we found two different burgus-related sedimentary facies, namely a lower moderate to high-energy fluvial facies right on top of Lower Terrace sands and a subsequent fluvial facies reflecting a clearly reduced flow velocity. The final phase of use of the burgus was dated to the time period 425-599 cal AD. It was thus in use for maximum 235 or so years.

Our results yield evidence of a large lake environment that existed near the ancient site of Olympia which was so far unknown. The limnic sequence reveals considerable changes in the ecological conditions over time, based on Direct Push sensing, sedimentary and micropalaeontological analyses. Radiocarbon data show that the “Lake of Olympia“ existed from the 8th/7th millennium BC until, at least, the 1st century AD. The existence of the “Lake of Olympia” next to the cult site of Olympia has considerable historical, archaeological and geographical implications (e.g., as waterway or water supplier).

We present a rare multi-system FDEMI survey at a Roman burgus in Hesse (Germany). The dataset shows the benefits of EMI/ERT system combination for investigating archaeology and embedding paleolandscape.

We performed a research-oriented EU Erasmus+ Blended Intensive Program (BIP) with participants from four countries focused on North Frisian terp settlements from Roman Iron Age and medieval times. We show that the complex terp structure and environment can be efficiently prospected using combined magnetic and EMI mapping, and seismic and geoelectric profiling and drilling. We found evidence of multiple terp phases and a harbor at the Roman Iron Age terp of Tofting. In contrast, the medieval terp of Stolthusen is more simply constructed, probably uni-phase. The BIP proved to be a suitable tool for high-level hands-on education adding value to the research conducted in on-going projects.

Since medieval times, North Frisia (Schleswig-Holstein, Germany) has experienced large-scale natural and man-made geomorphological changes. First, Frisian settlers turned the coastal marshes and fenlands into arable land but also increased the region's vulnerability to flooding. Then major storm surges drowned wide areas in 1362 CE and 1634 CE and many (geo-)archives that could provide knowledge about medieval man-environment interactions and the overall appearance of the coastal landscape at that time were irretrievably lost.To better understand the natural palaeogeographical evolution and human intervention with the coastal environment, our research focused on the Trendermarsch polder (Nordstrand), that is one of few sites still reflecting the cultivated marsh landscape of the 13th to 14th cent. AD.Fieldwork comprised DEM analysis, geophysical prospection by electrical resistivity tomography (ERT), seismic reflection measurements, Direct Push (DP)-EC logging and coring to obtain high-resolution stratigraphic data. Sedimentary, geochemical and microfaunal palaeoenvironmental parameter (PEP) analyses of sediment samples allowed to calibrate geophysical and DP-EC results. Radiocarbon dating, archaeological age estimations and historical reports provided a geochronological framework.Results confirm the 12th cent. AD age of the Trendermarsch polder but also reveal distinct phases of channel incisions, that are likely related to extreme events. These tidal channels appeared to be a distinct gateway for storm surges and considerably influenced medieval to early modern land reclamation and cultivation measures. The Trendermarsch therefore sets an impressive example for the interplay of natural processes and man-made geomorphological changes and their consequences for a coastal landscape.

We performed geophysical and geoarchaeological investigations in the Wadden Sea off North Frisia (Schleswig-Holstein, Germany) to map the remains and to determine the state of preservation of the medieval settlement of Rungholt, especially its southern dyke segment, called the Niedam dyke. Based on archaeological finds and historical maps, Rungholt is assumed to be located in the wadden sea area around the island Hallig Südfall. During medieval and early modern times, extreme storm events caused major land losses, turning cultivated marshland into tidal flats. Especially the 1st Grote Mandrenke (or St. Marcellus’ flood), an extreme storm surge event in 1362 AD, is addressed as the major event that flooded and destroyed most of the Rungholt cultural landscape. Cultural traces like remains of dykes, drainage ditches, tidal gates, dwelling mounds or even plough marks were randomly surveyed and mapped in the tidal flats by several authors at the beginning of the 20th century. Due to the tidal flat dynamics with frequently shifting tidal creeks and sand bars, the distribution of cultural remains visible at the surface is rapidly changing, making it hard to create a comprehensive map of the cultural landscape by surveying. Today, the Niedam dyke area is fully covered by tidal flat sediments, depriving any remains from further archaeological investigation. Since little is known about the precise location or state of preservation of these remains, our investigation aimed at the rediscovery of the medieval dyke system and associated structure with modern and accurate geophysical, geodetical and geoarchaeological methods. Magnetic gradiometry revealed a large part of the medieval dyke, confirming two tidal gates and several terps connected inland with the dyke, providing a detailed example of a Frisian medieval dyke system. Based on our results, the so far inaccurate and incomplete maps of this part of Rungholt can now be specified and completed. Beyond that, seismic reflection profiles give a first depth resolving insight in the remains of the dyke system, revealing a severe threat to the medieval remains by erosion. The site is exemplary for the entire North Frisian coast, that was influenced by multiple flood events in the middle ages to modern times.

In ad 1362, a major storm surge drowned wide areas of cultivated medieval marshland along the north-western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. Initially, we deciphered long-term as well as event-related short-term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)-based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) were applied at vibracore locations to obtain in situ high-resolution stratigraphic data. In a last step, multivariate linear discriminant analysis (LDA) was successfully applied to efficiently identify different sedimentary facies (e.g., fossil marsh or tidal flat deposits) from the CPT and HPT test dataset, to map the facies' lateral distribution, also in comparison to reflection seismic measurements and test their potential to interpolate the borehole and CPT/HPT data. The training dataset acquired for the key site from coring and DP sensing finally allows an automated facies classification of CPT/HPT data obtained elsewhere within the study area. The new methodological approach allowed a detailed reconstruction of the local coastal landscape development in the interplay of natural marsh formation, medieval land reclamation and storm surge-related land losses.

Ancient Ostia at the mouth of the River Tiber into the Tyrrhenian Sea was largely significant for the economic supply of Rome. Ostia itself experienced an extraordinary period of prosperity in the second century AD. Starting in AD 42, a first new harbour at Portus was built by Emperor Claudius close to Ostia. It reached its full functionality under Emperor Trajan in the early second century AD, only. At Ostia itself, previous archaeological and geoarchaeological studies have brought to light a lagoon-type harbour at the western fringe of the city operating between the fourth and the second century BC in an artificially excavated harbour basin. From the second century BC onwards, a considerably smaller and shallower part of this western harbour basin was still in function as a fluvial harbour. So far, it was unclear whether Ostia’s western harbour was still in use when the harbour at Portus was set into function in the first to second century AD, or if the latter partially replaced Ostia’s harbour infrastructure. According to archaeological evidence, Ostia’s navalia-temple-complex, the main building at the eastern fringe of the western river harbour basin, was built in the second quarter of the first century AD. Was this prestigious harbour building erected although the associated harbour seemed to have been already given up before? We conducted detailed geoarchaeological investigations at the immediate western front of the navalia-temple complex. Results were compared with archaeological data obtained from excavations carried out in 2000/2001. A multi-proxy approach was used to reconstruct the history and evolution of the harbour. It was possible to identify subsurface structures and evaluate the local stratigraphy. Vibracoring brought to light a more than 1 m thick section of an opus reticulatum wall with parts of the original opus latericium on top. Such walls originally separated vaulted shipshed chambers of the navalia-temple complex at Ostia, which in turn formed the substructure of a temple complex located above it. Another core revealed the sedimentary infill of a former chamber of the building. Based on radiocarbon dating, the navalia was in use between the first and the fourth centuries AD with a water depth of maximum ca. 1.2 m at the immediate western front. This is in agreement with the date of construction of the navalia-temple complex in the second quarter of the first century AD. The relative sea level at that time was around 0.64 m below the present sea level. The harbour and the navalia were obviously accessible only for flat-keeled lighters and cargo boats. Larger cargo ships were either unloaded along the riverbank to the north of ancient Ostia (Hadler et al. 2019 ) or moored offshore, their freight being reloaded to smaller lighters. Chronostratigraphic data further show that the navalia-temple complex was in use until the second half of the fourth century AD. It was not before AD 355–363 or shortly afterwards, that the harbour site was abandoned. Ostia’s western river harbour was neither abandoned nor completely silted up before the harbour at Portus was established as previously assumed by other authors. Actually, the western front of the navalia-temple complex was hit by an extreme wave event, leaving a sand layer approx. 0.5 m thick, at or shortly after AD 355–363 which led to the final abandonment of Ostia’s western river harbour. This event is interpreted as a tsunami that may have hit the wider coastal region.

The 1717 Christmas flood is one of the most catastrophic storm surges the Frisian coast (Netherlands and Germany) has ever experienced. With more than 13,700 casualties it is the last severe storm surge with a death toll of this order. At the same time, little is known about the hydrodynamic conditions and the morphological effects associated with this storm surge. In this study, 41 potential dyke failures in the Province of Groningen (Netherlands) associated with the 1717 Christmas flood were systematically reconstructed and mapped by using historical maps and literature and by analysing the recent topography in search of typical pothole structures and sediment fans. The dimensions of the sediment fans as derived from the topography show a good accordance with the dimensions documented by vibracore profiles, direct push tests and electrical resistivity tomography data taken at three fieldwork sites. Moreover, the fan dimensions closely agree with the dimensions as simulated using a process-based morphodynamic numerical model for one of the three sites, the village of Wierhuizen. Consequently, the recent topography is still indicative for the locations and dimensions of dyke failures and sediment fans associated with the 1717 Christmas flood. Considering the large number of detected dyke failures (41) and the large dimensions of the potholes and particularly of the sediment fans up to a few hundred metres wide and up to 0.7 m thick, this study proves significant morphological effects of the 1717 Christmas flood on the mainland of the Province of Groningen. Based on the numerical simulation approach and the comparison with field data and field observations, a maximum seaward water level of 5 m NAP for the dyke failure at Wierhuizen during the Christmas flood can be derived. A similar maximum water level is indicated for the two other fieldwork sites Vierhuizen and Kohol, which is in good agreement with the maximum storm surge level of 4.62 m NAP historically documented for the city of Emden located almost 50 km to the east of Wierhuizen. The results of the current study demonstrate that the reconstruction of historical dyke failures based on (i) historical sources, (ii) recent lidar/high-resolution topographical data, (iii) multi-proxy sedimentary field data and (iv) hydro- and morphodynamic numerical simulations is a highly promising approach to derive hydrodynamic conditions and the morphological onshore response of the 1717 Christmas flood in the Province of Groningen. This knowledge is essential to improve our understanding of extreme storm surge dynamics, their influence on the coastal landscape and the associated hazards for the coastal population.

We present a case study of a bog showing how an integrated approach of multi-method geophysical sounding and local soil sampling can be used to identify, differentiate, and map organic sediments. Our study is based on ground-penetrating radar (GPR), electrical resistivity tomography (ERT) and shear-wave seismic (SH seismic) profiling applied to sediments of the former Lake Duvensee (northern Germany), nowadays a bog. This is a well-known locality for remains from the Mesolithic hunter-gatherers’ occupation that has been attracting archaeological and geoarchaeological research for100 years. The bog is embedded in low conductive glacial sand and is characterized by layers of different gyttja sediments (detritus and calcareous). The present study was conducted in order to identify the bog morphology and the thickness of the peat body and lake sediments, in order to understand the basin evolution. To validate the geophysical results, derived from surface measurements, drilling, soil analyses as well as borehole guided wave analysis of electromagnetic waves and Direct-Push (DP-EC) have been carried out and used for comparison. It turned out that each method can distinguish between sediments that differ in grain size, particularly between peat, lake sediments (gyttjas and mud) and basal glacial sand deposits. GPR is even able to separate between strongly and weakly decomposed peat layers, which is also clear considering resistivity variations in the ERT computation. From the association between geophysical properties and sediment analysis (e.g., water content and organic matter) different gyttjas were distinguished (coarse and fine) and seismic velocity was correlated to bulk density. Moreover, GPR and SH-wave seismics present different resolutions, confirming that the latter allows measurements, which are more focused on determining the extension of basal sand deposits, the depth of which is difficult to reach with GPR. Representative values of electrical resistivity, dielectric permittivity, and shear wave velocity have been determined for each sediment type and are therefore available to complete the investigation of wetland environments. Fine grained lake sediments were difficult to differentiate by the applied methods. This could be a result of high ionic concentration within the permanent groundwater body, partly masking the sediment properties.

Mycenaean chamber tombs are composed of air-filled burial cavities and, therefore, can be detected by non-invasive geophysical methods. In this study, an electrical resistivity tomography (ERT)-based approach was used to detect graves at three different sites in the area surrounding ancient Olympia. We collected ERT data at the necropolis of Mageiras-Kioupia, where a number of chamber tombs had already been located and partly excavated in order to ground-truth the ERT response for chamber tombs in different states of preservation. Near the village of Epitalio, a preceding archaeological survey discovered remains of a one chamber tomb in mid-slope position of a larger hill. There, we applied the ERT-approach, calibrated at Mageiras-Kioupia, to the tomb and detected ten more tomb candidates at this site. In addition to ERT, we carried out ground penetrating radar (GPR) studies at the Epitalio site. In general GPR, data are highly consistent with ERT results. We were thus able to localize an unknown, most probably Mycenaean cemetery where no systematic archaeological information previously existed. In the third area of investigation, the Dartisa plateau, no potential chamber tomb comparable to the ones excavated and measured at Mageiras-Kioupia and Epitalio were identified.