A.P. Oost1*, Y.T. van Popta2
1 Deltares & Utrecht University, This email address is being protected from spambots. You need JavaScript enabled to view it.
2 University of Groningen, This email address is being protected from spambots. You need JavaScript enabled to view it.
Introduction
The westernmost inlet of the Wadden Sea, the Marsdiep, is a relatively young tidal system if compared to the other Dutch inlets. This might also explain the present-day relatively large depth of the system.
Situation up to ca. 1000 A.D.
At the dawn of historical times, the Zuiderzee region consisted of several river-fed lakes, described as Flevo Lakes (Lacus Flevo) and largely uninhabited peatlands (Van Bavel, 2010). The lakes gradually increased in size due to erosion. The peats extended N of the present-day IJsselmeer area and functioned as a barrier between the North Sea and the lakes. The waterway to the W, the Oer-IJ closed around 200 BC and limited drainage of the lakes (Vos, 2015). Throughout the Roman period and Early Middle Ages, the lakes were (partially) drained by the Vlie tidal inlet, as can also be deduced from the name Lacus Flevo, at least since 400 BC or perhaps even since 700-1000 BC (Vos, 2015; Van Zijverden, 2017). Given the fresh water conditions and the lack of strong tides in the lakes, fresh water must have drained towards the Vlie tidal inlet via a stream, which is mentioned Nakala in historical sources. Calculations learn that this channel was at least some 10-20 km long and of limited width. Such a situation may well have existed up to the 8th century AD as the Vita Boniface (754-768 AD) indicates. By that time, the name of the region changed from Lacus Flevo into Almaere, meaning ‘all lakes’ and suggesting larger fresh water basins. The Vlie system was most likely an estuary.
The Maresdeop (817 AD) indicates either a “marsh stream” or a “sea deep”, leaving it unclear how the situation was. However, up to at least 800 AD the coast between Den Helder and Texel was probably situated some 10 km more to the W (Schoorl, 1973). Tides came up to Den Helder, but 4.5 km to the E the area was inhabited in the 8th, 9th and in the 11th-12th century (Woltering, 1998).
1000-1500 the formation of the Zuiderzee
As the erosion of the seaward protruding coast of Texel-Den Helder continued, the Marsdiep itself also retreated in a landward direction. This will have made the peaty landscape E of it more vulnerable to flooding. The Marsdiep inlet might have been situated at its present location around 1220 AD or earlier, but had a small tidal volume (Oost et al., 2003). Salt water reached the Balgzand area around 1200 AD. Somewhere between probably 1150 and 1300 AD the Vlie system was contacted which originally may have reached westward up to Wieringen. The expansion of the Marsdiep to the E led to strong changes in the western Wadden Sea and the Zuiderzee area, as oxygen-rich salt waters driven by tides, waves and storm surges burned the peat and drained and eroded it.
Due to the expansion of the Marsdiep the Aelmere became directly connected to the sea instead of via a stream. Initially, this must have led to high current velocities and strong erosion. During the expansion in the backbarrier of the Marsdiep the tides may have been amplified as they met the land on about a quarter tidal length, which added to the erosion. By the end of the Early Middle Ages, pioneers entered the vast peatlands of the Zuiderzee region and started large-scale reclamation and cultivation works. It had a negative impact upon the peatlands, resulting in compaction, dehydration and increased vulnerability against marine erosion. Between at least the 12th to 14th century heavy floods scourged the large vulnerable land areas, resulting in marine ingression and formation of the Zuiderzee (Vos, 2015; Van Popta, 2017; Van Popta et al., in prep.). Land loss occurred at a large scale in a.o. the Wieringermeer area, the Hoornse Hop, near Amsterdam, the Noordoostpolder region and south of the IJsseldelta. New research by Van Popta (2017) and Van Popta & Benders (in prep.) demonstrates the positive and negative consequences of these landscape dynamics: multiple settlements drowned (e.g. Nagele, Marcnesse, Venehusen) while important maritime trade routes were established (e.g. Rhine - IJssel – Zuiderzee – North Sea – Baltic Sea). At the same time the area became brackish marine. Erosion continued throughout the Late Middle Ages, but was limited by the construction of dikes from the 13th century onwards.
REFERENCES
Bavel, B., van, 2010. Manors and Markets. Economy and Society in the Low Countries, 500-1600. Oxford: Oxford University Press.
Oost, A.P., S. van Heteren, J. Wallinga & M. Ballarini, 2003. De Kalender van Texel op basis van luminescentie en historische gegevens, excursiegids, RIKZ/AB/2003.603x
Popta, Y.T., van, 2017. Opgespoorde sporen van bewoning. Een archeohistorische en geografische interpretatie van het laatmiddeleeuwse landschap van de Noordoostpolder. Tijdschrift voor Historische Geografie 2.3, 130-143.
Popta, Y.T., van & J.F. Benders, in prep. Maritime farmers on the run. Consequences of the rise of the Zuyder Zee (the Netherlands) from an archaeohistorical point-of-view (AD 1100-1400). Journal of Maritime Archaeology.
Popta, Y.T., van, K.M. Cohen, P.C. Vos & Th. Spek, in prep. Reconstructing medieval eroded landscapes of the Northwestern Zuyder Zee (The Netherlands): towards a refined palaeogeographical time series of the Noordoostpolder between AD 1100 and 1400. Landscape History.
Schoorl, H., 1973. Zeshonderd jaar water en land. Bijdrage tot de historische Geo- en Hydrografie van de Kop van Noord-Holland in de periode 1150-1750. Verhandeling van het Koninklijk Nederlands Aardrijkskundig Genootschap, Nr.2, Wolters-Noordhoff, Groningen, 534 pp.
Vos, P.C., 2015. Origin of the Dutch Coastal Landscape. Long-term landscape evolution of the Netherlands during the Holocene, described and visualized in national, regional and local palaeogeographical map series. Thesis (PhD). Utrecht University.
Woltering, P.J., 1998 (1996–1997). Occupation History of Texel, III: The Archaeological Survey, Paleodemography and Settlement Patterns, BROB 42, 209–363.
Zijverden, W.K., van, 2017. After the Deluge. A Palaeogeographical Reconstruction of Bronze Age West-Frisia (2000-800 BC). Thesis (PhD). Leiden University.
