Post on 22-Oct-2021
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
X
X X
X
√
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.