Five Centuries of Fluvial Dynamics and Environmental History of the Danube Floodplain, Southern Hungary: Insights from Historical Maps

The fluvial dynamics of the Danube in the Mohács Island region (Southern Hungary) were analyzed using historical maps spanning the last 500 years. Battle of Mohács, the defeat of the Hungarian armies by the Ottoman Empire took place here in 1526, in environmental conditions that are quite different from today. To reconstruct these conditions, the behaviour of the Danube, the main influencing factor has been studied.

Numerous historical maps, like Tabula Hungariae (1528), Marsigli’s (1726), Müller’s (1709), Lipszky’s (1803) and Korabinszky’s (1804) maps together with the three Military Surveys of the Habsburg Empire (1782-1887) have been transformed or georeferenced and integrated in QGIS for analysis. River branches have been digitized and compared to the present-day situation represented in satellite imagery and a digital elevation model.

Apart from comparing the channels of different centuries, sinuosity values of the river branches and oxbow lakes were calculated. The results provide insights into the river's meandering behaviour and its environmental evolution. Although meandering is the dominant in this section, historical evidence indicates a period when the Danube exhibited an island-building phase. During this time, unlike today, the eastern branch of the river marked the main channel, shaping the floodplain. 

Quantitative analyses demonstrated a general declining trend in sinuosity due to the narrowing of bends, river self-regulation, and recently, human-induced interventions such as river regulation. The persistence of island-building period was likely linked to variations in sediment yield and flow patterns. Historical maps suggest that inflowing streams may have had more discharge during this period, contributing to higher sediment deposition at reduced velocities, particularly when the eastern branch served as the main channel. The eventual reversal of the main branch is attributed to flooding events that redefined the fluvial network. 

To ensure the reliability of the reconstructions, the accuracy of old maps was also evaluated. The oldest maps depicted rather the character of the river branches, but advances in cartography significantly reduced distortions, enabling the reconstruction of former river courses with greater precision. Comparisons with contemporaneous maps and topographical models highlighted minor deviations and resulted in revision of a few former interpretations. 

The study also identified key areas where flooding or marshland characteristics could have influenced land use and military strategies, underscoring the broader implications of environmental history in shaping the region's past. This work highlights the critical role of historical cartography and environmental analysis in understanding long-term fluvial transformations and their socio-environmental impacts.