Little Ice Age, Palaeofloods and human adaptation on the Jarama River (Tajo Basin, Central Spain) from documentary proxy data

Abstract

This research assesses the close relationship between river history and human adaptation by combining the study of the migration of channels on the floodplain, the temporal distribution of floods, and human adaptation to the fluvial environment during the Little Ice Age (LIA) period on the Jarama River section situated between the mouths of two tributaries, the Henares and Manzanares. The methodology consists of the employment of abundant documentary records from the 14th to 19th centuries related to the response of society to hydrological dynamics within changing river patterns. The management and delimitation of land ownership, along with the readjustments and modifications therein, allow the inference of the changes that have taken place in the river throughout history. These changes include meander cut-offs, the abandonment of a channel fragment and aggradation in the alluvial plain, all of them located in different areas within the study area and with different historical timeframes. A relationship exists between changes in fluvial dynamics and the times of the greater abundance of floods. An initial change in the alluvial plain occurred in the Middle Ages as a result of the abandonment of the medieval channel and the creation of a new channel. The second change occurred between the 15th and 17th centuries and affected the properties on the right-hand bank of the river. Since the 18th century, the abandonment of and reduction in meanders and the aggradation at the Manzanares-Jarama mouth have created a new alluvial plain of the river. The different phases of the LIA defined herein coincide with much of the palynological and dendrochronological research conducted in other areas of the southwestern fringe of Europe. From the historical point of view, critical changes appear to be associated with some LIA phases. Furthermore, the progressive transformation of communal lands into public or private property could be promoted by the intense floods recorded since the 15th century. The Maunder and Dalton Minimums occurred together with an increase in the area assigned for agriculture on the alluvial plain; this land use type continued to grow during the 19th and 20th centuries.