3D modelling of Holocene groundwater level rise in two drowned Rhine valleys in the Netherlands

3D modelling of Holocene groundwater level rise in two drowned Rhine valleys in the Netherlands

Kay Koster ^1,2 , Jan Stafleu ² , Kim Cohen ^1,2,3

1 Utrecht University, Dept. of Physical Geography 2 TNO Geological Survey of the Netherlands 3 Deltares BGS, Dept. of Applied Geology and Geophysics

workflow

results showing the drowning of the two valleys during the Holocene

target area

We present a full 3D interpolation describing groundwater rise in two neighboring river valleys based on age- depth relations of basal peat index points

for GW levels through the Holocene.

Rapid drowning 9000 to 8000 cal BP occurred relatively synchronous in the

two valleys, explained by strong sea- level rise control and similar valley

gradients and dimensions of the

inundated valley sections. After 8000 the drowning history diversifies. From then

on a strong river gradient is in effect in the Rhine delta (valley 1), and absence

of a larger river keeps gradients near sea-level far inland in the northern valley

(valley 2). Varying valley slopes explain further differences. Via GW rise effects,

the palaeovalley dimensions are an important control on Holocene

transgressive landscape development.

10000 cal BP 9000 cal BP 8500 cal BP 8000 cal BP

7000 cal BP 6000 cal BP 5000 cal BP

4000 cal BP 3000 cal BP 2000 cal BP 1000 cal BP

two palaeovalleys

1

2

Location 20 meters under

water! symposium