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/

Questions or comments?

renske.hoevers@kuleuven.be