A large‐scale medieval dam‐lake cascade in central Europe: Water level dynamics of the Havel River, Berlin–Brandenburg region, Germany

Abstract

An interdisciplinary study was carried out to trace the hydrological changes of the Havel River in northeastern central Europe over the last ca. 2000 years. This research was driven by the hypothesis that the present‐day riverscape is to a large degree a result of medieval and modern human transformation of the drainage system. The river system forms a series of dammed lakes and river sections that were greatly altered through hydraulic engineering in the past. Along the middle course of the Havel, 16 sedimentary sequences available for geoarchaeological and paleoecological research were analyzed in order to reconstruct regional water level dynamics. Chronological control was ensured through a multitude of palynological, dendrochronological, archaeological, and radiocarbon data. The sections upriver from the Brandenburg/H. and Spandau weirs, representing sites with historic watermills, reveal substantial water level changes during the late Holocene. Generally, lower water levels before and higher levels during the medieval German colonization of that area (ca. A.D. 1180/1250) can be inferred. This water level increase, which is primarily attributed to dams constructed for watermills and secondarily due to a multitude of fish weirs, took place rapidly and amounted to a relative height of ca. 1.5 m. It enlarged the river's cross‐sections and increased the size of existing lakes or initiated secondary lakes that previously aggraded, and thus caused flooding of large parts of land. The rising water level even influenced the settlement topography to a large degree. Several medieval rural settlements were abandoned due to flooding. In total, a ca. 150‐km long dammed lake cascade was formed.

Influence of 200 years of water resource management on a typical central European river. Does industrialization straighten a river?

“…In the early Holocene, rivers were mainly anabranching, which changed in the late Holocene [3]. While geomorphologic changes before the late Holocene are mainly attributed to climatic factors [4,13], the establishment of agriculture and large-scale deforestation in the Neolithic period led to a tipping point [14,15]. Increased human land use has led to siltation of secondary channels, which changes river morphology [3].…”

Archaeological dating of colluvial and lacustrine deposits in a GIS environment investigating the multi-period site Gortz 1 on Oberer Beetzsee, Brandenburg

“…They are referred to in this study as the upstream and downstream water. The most recent study assumes that the dam system caused a water level rise of 1.5 m in the upstream water (Kaiser et al, 2018). However, the Beetzsee chain of lakes drains into the river Havel downstream from the dam system ( Fig.…”

“…In a second step, the profile was tilted from the profile view to plan view. A matrix multiplication in Excel served as an aid for this process, in which points with xyz coordinates can be rotated around the three spatial axes (X, Y , Z) at will (Kühnlein, 2019). This manipulation of the coordinates becomes necessary if the profile is not aligned with one of the cardinal axes (north-south = Y , west-east = X) shown in Fig.…”

“…The introduction of new technologies, such as the heavy plough, or the founding of new towns, led to far-reaching changes on the economic and infrastructural level (Brather, 2001). Large-scale agricultural cultivation, damming and hydro-melioration projects began to influence the water level of the middle and lower Havel, which led to lasting changes that are still visible in the landscape today (Kaiser et al, 2018). This raises the question of the extent to which the Gortz site was affected by these changes.…”

Changes in the Dynamics and Nature of Sedimentation in Mill Ponds as an Indicator of Environmental Changes in a Selected Lake Catchment (Chełmińskie Lake District, Poland)

“…However, bottom sediments related to the functioning of water mills were analyzed by other researchers in the context of the role of mill dam in regional erosion and sedimentation [33]. Also, along the middle course of the Havel, sedimentary sequences available for geoarchaeological and paleoecological research were analyzed in order to reconstruct regional water level dynamics [34]. The objective of a study in Germany (Wurm River) and in the Netherlands (Geul River) was to determine how the construction and later removal of water mills had influenced the longitudinal bed profile of a river and its floodplain sedimentation [35].…”