UNDERSTANDING THE FINE SEDIMENT BUDGETS OF RIVER …

UNDERSTANDING THE FINE

SEDIMENT BUDGETS OF RIVER

BASINS

DES WALLING

College of Life and Environmental Sciences

Karlsruher Flussgebietstage 2013, June 20-21, 2013 - Solids in River Basins

Erosion and Sediment Yield: An Unfashionable Research Area

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A New Importance

From:

Vanmaercke et al. (2011) Sediment

yield in Europe: Spatial patterns and

scale dependency.

Improved Understanding of the System

New Information Requirements

Sediment Sources

Sediment Delivery – Connectivity

Sediment Sinks and Storage

Sediment Budgets

Sediment Management

THE SEDIMENT

BUDGET

After Stan Trimble

360 km2

THE NEED FOR NEW APPROACHES

• Sediment Sources

• Sediment Mobilisation and Delivery

• Sediment Storage

(Tracing Techniques )

What rather than How

Sediment Source Fingerprinting

Sediment Source Fingerprinting

Two Examples:

• Establishing the relative importance of different sediment

sources in UK catchments (Sediment Management: EU

Water Framework Directive)

• Assessing the effectiveness of improved land management

strategies - Rio Grand do Sul, Brazil

POTENTIAL SEDIMENT SOURCES

• Channel banks / subsurface sources

• Surface soil from cultivated areas

• Surface soil from pasture areas

• Surface soil from woodland areas

Time-Integrating trap samplers

Suspended Sediment Sources in the Wye and Hampshire Avon Catchments, UK

The Wye

The Hampshire Avon

Potential fingerprint property

H-value P-value

Al 17.622* 0.001*

C 40.143* 0.000*

Ca 1.815 0.612

Cd 37.662* 0.000*

Co 1.031 0.794

Cr 25.788* 0.000* 137Cs 52.171* 0.000*

Cu 22.305* 0.000*

Fe 9.542* 0.023*

K 37.820* 0.000*

LOI500 59.472* 0.000*

LOI850 0.891 0.828

Mg 12.692* 0.005*

Mn 39.571* 0.000*

N 60.952* 0.000*

Na 22.822* 0.000*

Ni 10.000* 0.019*

IP 12.696* 0.005*

OP 7.450 0.059

TP 14.067* 0.003*

Pb 10.446* 0.015* 210Pb 18.172* 0.000* 226Ra 8.228* 0.042*

Sr 2.302 0.512

Zn 11.183* 0.011*

Step Fingerprint property selected

% Source type samples

classified correctly

1 137

Cs 55.7

2 Mn 67.9

3 Cd 75.5

4 Ni 81.1

5 IP 84.0

6 Cr 86.8

7 N 86.8

8 Al 87.7

9 Cu 89.6

10 K 90.6

11 LOI500 93.4

Statistical Testing of Source Discrimination

THE ARVOREZINHA CATCHMENT, BRAZIL

1.19 km2

b) a)

Ongoing Development of

Source Fingerprinting Techniques

• Standardisation for particle size

and organic matter content

• Statistical testing for source

discrimination

• Establishing optimum composite

fingerprints

• Improved mass balance modelling

• Inclusion of uncertainty

Source: Adrian Collins, ADAS, UK

• New fingerprint properties

SEDIMENT MOBILISATION

AND DELIVERY

Use of Fallout Radionuclide Tracers

Radionuclide Origin Half-life Time Window

137Cs Man-made 30.2 yr. ~ 50 years

210Pbex Geogenic 22.3 yr. ~ 100 years

7Be Cosmogenic 53.3 days ~ 1 month

FREE TRACERS

Key Features of the Approach

RETROSPECTIVE

TIME INTEGRATED

SINGLE SITE VISIT

OPPORTUNISTIC

SPATIALLY DISTRIBUTED DATA

The Field-scale approach

Collection of Soil Cores using

a grid sampling network (140 cores 20m x 20m grid)

Establish Reference Inventory

Compare Core Inventories with Reference Inventory

Estimate Soil Redistribution Rates

(6.7 ha)

Past 55 years

RATES OF SOIL REDISTRIBUTION WITHIN THE

STUDY FIELD ESTIMATED FROM

Cs-137 MEASUREMENTS

Measure

Range of redistribution rates

Mean erosion rate for eroding areas

Mean deposition rate for depositional areas

Net soil loss

Sediment delivery ratio

(kg m-2 year-1)

- 4.5 to +2.0

-1.1

0.69

-0.48

0.83

UPSCALING TO CATCHMENT AND RIVER BASIN SCALE ?

1.47 ha

139 ha

3161 ha 68 Bulk Cores

110 Replicate Bulk Cores

128 Replicate Bulk Cores

Using Low Density Sampling of 137Cs inventories

to Investigate Soil Redistribution within small

and intermediate sized catchments

Porto, P., Walling, D.E. and Callegari, G. (2011) Using 137Cs

measurements to establish catchment sediment budgets and

explore scale effects. Hydrological Processes 25, 886-900.

RIVER BASIN SCALE ?

A National Scale Investigation

Extrapolating field-scale estimates of soil erosion rates

• Refined sampling protocols - To obtain reliable and

meaningful estimates of the soil erosion rates within a

particular field based on a small number of cores

• Sampling a range of fields - To obtain

information on the range of soil erosion rates and the

influence of key controls

• Extrapolation of the results

Walling, D.E. and Zhang, Y. (2010) A

national assessment of soil erosion based

on caesium-137 measurements. Advances

in Geoecology 41, 89-97.

The Study Area

Excludes forest areas, urban areas, areas of

open water, flat areas (< 1 degree slope),

upland areas (>300 m) and National Parks

The Sampling Locations Includes 248 fields

A National Scale Soil Erosion Inventory

Slope Gradient

HER

Soil Management

Group

Erosion Risk

Documented

Erosion Rates

248 fields

NATIONAL SCALE

EXTRAPOLATION

The typology used for

extrapolating the field scale

erosion rate data to the

national scale (Boxes with bold text

Indicate existing datasets)

A national map of net

erosion rates for a

combination of cultivated

and pasture land use

Suspended Sediment Yield Soil Erosion Rates

Source: Natural England

Suspended sediment yield (t km-2 year-1) Gross erosion (t km-2 year-1)

CONNECTIVITY: A National Scale Assessment

Based on Walling & Zhang (2004)

SEDIMENT STORAGE

Floodplain Sedimentation Rates?

MEAN ANNUAL FLOODPLAIN SEDIMENTATION RATES ESTIMATED FOR

REPRESENTATIVE SITES ON 21 BRITISH RIVERS USING Cs-137 AND

EXCESS Pb-210 MEASUREMENTS

River and location

1 River Ouse near York

2 River Vyrnwy near Llanymynech

3 River Severn near Atcham

4 River Wye near Preston on Wye

5 River Severn near Tewkesbury

6 Warwickshire Avon near Pershore

7 River Usk near Usk

8 Bristol Avon near Langley Burrell

9 River Thames near Dorchester

10 River Torridge near Great Torrington

11 River Taw near Barnstaple

12 River Tone near Bradford on Tone

13 River Exe near Stoke Canon

14 River Culm near Silverton

15 River Axe near Colyton

16 Dorset Stour near Spetisbury

17 River Rother near Fittleworth

18 River Arun near Billingshurst

19 River Adur near Partridge Green

20 River Medway near Penshurst

21 River Start near Slapton

Past 33 years

0.95

0.21

1.22

0.15

0.86

0.46

0.88

0.39

0.51

0.70

0.60

0.56

0.45

0.35

0.51

0.04

0.11

0.39

0.51

0.15

0.51

Sedimentation rate (g cm-2 year-1) Past 100 years

1.04

0.46

1.42

0.28

0.95

0.66

1.01

0.33

0.64

0.93

0.65

0.43

0.42

0.32

0.40

0.04

0.14

0.48

0.71

0.23

0.45

Trend*

Stable

Decrease

Decrease

Decrease

Stable

Decrease

Decrease

Increase

Decrease

Decrease

Stable

Increase

Stable

Stable

Increase

Stable

Decrease

Decrease

Decrease

Decrease

Increase

*Increases and decreases are identified as cases where recent (33 year) sedimentation rates deviate by more than ±10% from the 100 year value

River Ouse, Yorkshire, UK

River Conveyance Loss

Swale 31%

Ure 34%

Nidd 50%

Total Ouse 40%

Wharfe 49%

Floodplain Conveyance Loss?

River Ouse

Yorkshire

Sediment Flux

CONSTRUCTING THE SEDIMENT BUDGET

In-Field Storage

Pang & Lambourn Catchments, UK

Catchment Sediment Budgets

THE PROSPECT

• Valuable new tracing techniques

• Scale Problems

• Diverse Landscapes – Generalisation

• Links to Modelling

Acknowledgements

THANK YOU

Adrian Collins

Yusheng Zhang

Paolo Porto

Jean Minella

et al.