holocene alluvial floodplains in belgium: from natural to
TRANSCRIPT
Renske Hoevers, Nils Broothaerts, Ward Swinnen, and Gert Verstraeten
KU Leuven - Earth & Environmental Sciences
Holocene alluvial floodplains in Belgium:
from natural to human dominated environments
• Early/Middle Holocene: most floodplains
were stable environments with limited
floodplain aggradation, resulting in peat growth
• Late Holocene: floodplains changed
completely towards single channel meandering
rivers with overbank deposits, impeding peat
accumulation
• Transformation in floodplain geoecology is
largely a result of increasing anthropogenic
impact, hence timing can differ a few
thousand years between different river valleys
2
Early/Middle Holocene
Late Holocene
Holocene alluvial floodplain
evolution and its drivers
Local changes in
floodplain geoecologyRegional drivers based on (semi)-quantitative analyses of
pollen data from the floodplains
REVEALS NMDS
KempenDijleGeteMombeek
• During the Neolithic
Period and the start of
the Bronze Age: local
scale human impact and
limited connectivity to the
fluvial system
• From the Bronze Age
onwards: decrease in
forest cover and increase
in agriculture more
erosion in the area
more sediment deposition
in the river valleys
impeding peat growth in
the floodplains
• From the Neolithic period onwards, deforestation is
detected in both the loess and sandy region, although
the loess belt underwent a more rapid and severe
reduction of woodland
• While this deforestation is accompanied by an
increase in cropland in the loess region from the
Bronze Age onwards, the sandy region only starts
to show limited agriculture from the Iron Age
onwards, related to its later and less dense human
occupation
• While the amount of records and their resolution is
rather low in the sandy region, the numerous and
detailed records of the loess belt also allow
detection of more local and short-term effects
(< 200 years) of changes in human impact
Local changes in
floodplain geoecologyRegional drivers based on (semi)-quantitative analyses of
pollen data from the floodplains
REVEALS NMDS
KempenDijleGeteMombeek
• Early Medieval Period:
decrease in human impact
allows the regeneration of
vegetation barriers
lowering sediment input
reactivation of peat
growth and regrowth of
the alder-carr floodplain
vegetation
• After this temporary
decrease, human impact
increased again and the
evolution towards open
floodplains with single-
channel rivers resumed
Local human intervention
in the floodplains
• After this temporary decrease, human
impact on floodplain geoecology started
to increase again up till modern times
• The impact also got more direct, not
only by altering the course of the rivers;
• peat extraction from the floodplains
became common practice, especially
in the sandy Campine region
• Often, this is difficult to detect as the
holes were filled up again with sand, to
rapidly create useful pastures
https://www.futurefloodplains.be/
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