The history of the Amstel and Vecht rivers in the central part of the Netherlands during the Holocene has been debated for a considerable time (Bos et al., 2009; De Bont, 1994, 2000, 2008; De Bont & Kleij, 2012; De Gans, 2011; De Gans & Bunnik, 2011, 2012). Many publications in different disciplines have made their contribution to solve issues such as initiation and cessation of river flow, different and opposing river flow directions, and different chronologies.

The prehistoric Oer-IJ tidal system in the coastal area of Noord-Holland, between Castricum, Uitgeest, Velsen and Amsterdam, was the successor of the Haarlem tidal system when this was silted up around 3000 BC and large peat bogs formed in the Zaanstreek and Haarlemmermeer areas. Since then the Oer-IJ has been the natural outlet to the sea, draining the peat hinterlands. About 800 BC the Oer-IJ system was connected to the fluvial system of the Utrechtse Vecht and became the northern branch of the river Rhine. During the Late Iron Age, when the Flevo lakes in the IJsselmeer region and the Utrechtse Vecht were connected with the Wadden Sea, the Oer-IJ lost its discharge function. The tidal area silted up and was closed between 200 and 100 BC by a barrier ridge. The settlement history of the Oer-IJ system and the archaeological heritage in the subsurface is closely related to the geological and hydrological development throughout the ages. The shape and location of the continuously migrating outlet determined the opportunities for human settlements and activities. The best locations were beach ridges, higher, silted-up salt marshes and marginal zones of the peatland. In the Late Iron Age the sand flats also became habitable since tidal activity had stopped. In the Early Roman period there was no direct connection from the harbour of Castellum Flevum at Velsen to the North Sea, but ships could navigate from the Oer-IJ channel between Velsen and Amsterdam, through the Flevo lakes and the Utrechtse Vecht to the Wadden Sea, and to the Roman border (Limes) along the Oude Rijn. Here the data used for the palaeogeographic landscape reconstruction of the Oer-IJ are presented and explained, and the most important landscape-forming processes, which led to the emergence and closure of the Oer-IJ, are described. The landscape reconstructions give a new perspective on the migration of the main tidal channel and the formation of the tidal-inlet system near Castricum, which was the result of the progradation of the beach ridges south and north of the Castricummerpolder (Binnendelta according to De Roo, 1953). The geological and archaeological observations in the Binnendelta prove that the Oer-IJ was closed from the open sea in the early Late Iron Age.

Since 2003 extensive archaeological research has been conducted in Amsterdam, the Netherlands, connected with the initial phase of the new underground system (Noord/Zuidlijn). Research has mainly focused on two locations, Damrak and Rokin, in the centre of Medieval Amsterdam. Both sites are situated around the (former) River Amstel, which is of vital importance for the origin and development of the city of Amsterdam. Information on the Holocene evolution of the river, however, is relatively sparse. This project has provided new evidence combining archaeological and geological data, and allowed the reconstruction of six consecutive landscape phases associated with the development of the River Amstel. The course of the present-day Amstel is the result of a complex interaction of processes that started with an early prehistoric tidal gully within the Wormer Member of the Naaldwijk Formation, including Late Neolithic (2400–2000 BC) occupation debris in its fill that was subsequently eroded. Next, this system developed into a later prehistoric Amstel river course that was part of the Angstel–Vecht–Oer-IJ system (1020–350 BC), meandering through a peat-dominated landscape. Later on the processes included intensive reclamation of land, drainage and canalisation, although the Amstel was also strongly influenced by natural storm tides. After intense land reclamation, starting around 1200 AD, the meandering Amstel from Nes to Kalverstraat, which was originally 150 m wide, became the rather straight 20–50 m wide tamed, canalised river of today.

Around 800 AD the peatlands around Amstelland were drained by two rivers. The ‘northern’ Amstel discharged surplus water directly into Lake Almere, which from the 12th century onwards was enlarged to form the Sudersee (in Dutch: Zuiderzee). The ‘southern’ Amstel was a near-abandoned westernmost arm of the River Vecht discharging the poorly drained borderland around the river Vecht into Lake Almere/the Sudersee. As part of the reclamation of peatlands associated with agricultural activities between the end of the 10th and the mid-13th centuries, the rivers were connected via a canal, thus creating the river Amstel, as it is known today.

The Amstel river is located in the peat-covered coastal plain of the Netherlands and gives Amsterdam its name (Amstel dam). It is a small secondary branch of the repeatedly bifurcating Rhine delta system. Historically, the Amstel debouched into the peat-fringed former Oer-IJ estuary, which was connected to the North Sea, but after the closure of this inlet the estuary was transformed into an inland sea (IJ) due to erosion of the adjacent peat. The Amstel river was active between 3000 BP and 1122 AD after which time the supply water from the Rhine was stopped due to the construction of a dam far upstream near Wijk bij Duurstede. On the basis of borehole data from various sources, four cross-sections were constructed in the Amstel branch to study the unknown lithology and lithostratigraphy of the Amstel sediments in the Amsterdam area. The deposits show the Amstel was a low-energy river which carried mainly clay. The cross-sections reveal that the Amstel in its downstream part was flanked by two lithologically identical layers of overbank clay, intercalated by a peat layer. The lowermost overbank clay was deposited from 3000 BP to about 1000 AD. The intercalated peat layer is estimated to have developed between the 11th and 12th centuries AD, indicating a decreased sediment supply in the Amstel, and rise of water level in the downstream river caused by Zuiderzee influences such as storms and tide. The uppermost overbank clay was deposited during major storm surges such as those documented in 1164 and 1170 AD, and was derived from the brackish Zuiderzee; it has been traced upstream along the Amstel for over 10 km. Near the mouth of the Amstel channel in the Oer-IJ estuary its bottom has been scoured by estuarine processes to a lower level. On the basis of archaeological and geological data it is argued that the Amstel channel of medieval Amsterdam had a water depth of about 6 m before the construction of a dam in the 13th century. Soil scientists, historical geographers and historians have argued that the Amstel once consisted of two separate rivers: a northern Oer-IJ connected channel draining from the Amsterdam Stopera to the north, and a southern peat draining channel draining from the Amsterdam-Watergraafsmeer to the south. The relatively straight stretch of the present-day Amstel now positioned within the urban area has been hypothesised to be man-made between the 11th and 13th centuries AD. In this paper, on the basis of geological arguments such as channel depths, overbank clays, peat composition and other characteristics, it is concluded that the Amstel had a natural channel in the Amsterdam area.

Based on historical evidence a description in broad outline is provided of landscape and settlement development in the Vecht area north of Utrecht for the period 722–1122 AD. Although the fluvial activity of the Vecht channel was reduced from about 2300 BP onwards, the river retained its economic importance as a shipping route in Early Medieval times according to the appearance of mintage and the spread of tollhouses. In the 8th century the Vecht still was seen as a river and as a branch of the Rhine. At that time the Vecht river discharged into a stretch of water that was named Almeer and was characterised as stagnant. The Almeer is regarded as the successor of Lake Flevo, mentioned by classical authors. Since this body of water is indicated as stagnum, it is unlikely that the water level in the southern part of the Almeer was affected by the Vlie tidal inlet in the north at that time. At the end of the 10th century the Almeer already had substantial dimensions. The building of dikes on the southern forelands of the Zuiderzee and the IJ-Lake started at least about 1200 AD. At the beginning of the timeline, settlement was limited to the natural levees of the river Vecht and its distributaries. The reclamation of the vast peatlands on both sides of the river started around the middle of the 11th century. The opening up of new areas for agriculture and settlement was accompanied by a transformation of the social fabric. In association with the pattern of land division historical information is used to indicate some of the changes that occurred in the Vecht area during that period. The drive to further intensify land use resulted in 1122 AD in the decision to build a dike on the northern bank of the Lower Rhine, since the Vecht is a blind arm of the river Rhine.

A solitary unprocessed, 26-cm basalt stone recently found at the Roman (69 AD) site at Kotterbos (Lelystad, the Netherlands), situated 40 km north of the Limes, has been examined petrographically and geochemically. The rock is similar to previously investigated Roman basalt stones and blocks from the Limes in the province of Utrecht. All are alkali olivine basalts and basanites, which are also the dominant rock types in the nearby volcanic hinterland in Germany. On the basis of 23 criteria, including all major and minor elements plus a selection of trace elements, the Kotterbos stone correlates with a distinctive subgroup of Limes basalts. This subgroup is characterised by relatively high Mg# and low TiO2 wt% values, as opposed to the other subgroup with lower Mg# and higher TiO2 wt% values. It is argued that the high Mg#–low TiO2 subgroup and the Kotterbos basalt have common geological provenance(s). Five basalt bodies in the hinterland match the criteria of this subgroup, and might be considered as locations of provenance. Of these five, only Rolandsbogen, located next to an ideal anchorage on the west bank of the Rhine, about 12 km upstream from Bonn, can also conform to sensible Roman demands concerning effective logistics and military safety. Consequently, Rolandsbogen is the most likely site of provenance for the high Mg#–low TiO2 subgroup, which includes the Kotterbos basalt. It is argued that the Kotterbos stone is not a rock that somehow got separated from a shipment of building stones to the northern Limes; rather, it is speculated that the stone was picked up as a stray cobble near the basalt body and taken onboard a Roman vessel moored at the Rolandsbogen anchorage.

Amsterdam is situated on the coastal-deltaic plain of the western Netherlands. Its geographical position brought the city prosperity, but also created huge challenges associated with heterogeneous and often adverse ground conditions. This paper explores the geology of Amsterdam to a depth of c. 100 m, based on the output of the 3D geological subsurface models DGM and GeoTOP. The model results are used to create a geological map of the area, to determine the extent and depth of the foundation levels that are in use for buildings in the city centre and to detect the source of filling sand on which part of the more recent expansion of the city was founded. It is shown that subsurface conditions have had a profound effect on both landscape development and historical city growth. Geomodels like DGM and GeoTOP provide an easily accessible way to obtain a better understanding of the shallow subsurface.