‘Soil Erosion Modelling’ Workshop, JRC Ispra, March 21, 2017.

The use of radionuclides for improving modelling of soil erosion and sediment transfer:

Lessons learnt from various case studies

Olivier Evrard, J. Patrick Laceby, Irène Lefèvre, and many colleagues from other labs

• Need to better identify sediment sources and transfer times in catchments

• Radionuclides having a strong affinity for fine particles and characterised by different half-lives provide a powerful tool

SLOW BOX (SOIL)

INPUT (rainfall)

OUTPUT (river)

Introduction

FAST BOX (RIVER)

Dominik (1987) Developmentof box models

Matisoff (2005) Developmentof ratios

Introduction• The use of the 7Be/210Pb ratio has been associated with several

limitations

• The method would be applicable to the material exposed to atmospheric fallout

Surface exposed to fallout

137

Cs% SURFACE

% SUBSURFACESubsurface shelteredfrom fallout

Pilot study site (monsoon climate)

Surface area 22 km²

Improving the method• Quantifying the contributions of four sources to avoid these limitations

•A mixing model based on distributions provides the relative contributions of these four sources to river sediment:

MMD = �i=1

n

Ci − �s=1

m

PsSsi /Ci

n is the amount of radionuclides used by the model;Ci is the normal distribution of radionuclide (i) in river sediment; m is the number of sources in the catchment; Ps is the mixing distribution of source contributions; Ssi is the normal distribution of radionuclide (i) in source (s).

Laceby et Olley , Hydr. Proc. (2014)

Subsurfaceold

Subsurfacerecent

Surface old

Surface recent

Source contributions – flood of June 2014S1

S4S10

At the upstream station (S4), surfacesources are dominant (55%).

Downstream (S10), subsurface sources are dominant (74%). 60% of ‘recent’ material !

Evrard et al., JSS (2016)

This method provides new insights into sedimentsources and transfer times in contrasted environments

Fukushima coastalcatchments (Japan)Dilution of radioactive contamination

Seine River (France)

Loire River(France)Sediment behaviourin drained catchments

Big flood (June2016) in Paris

Andes(Peru)

Consequences of the peatland cultivation

(In progress)

(In progress) Le Gall, Sc. Rep. (2017)Evrard, Sc. Rep. (2016)

Many thanks for your attention!

olivier.evrard@cea.fr27 mars 2017

Slide Number 1Slide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8