Presentation given at the 2nd SILTFLUX workshop on 19/05/2015 at UCD. Authors: Iwan Jones, Adrian Collins, John Murphy, David Sear, Pam Naden

1. Managing the impact
of fine sediment on
river ecosystems
Iwan Jones, Adrian Collins, John
Murphy, David Sear, Pam Naden

2. Erosion and Deposition are Natural Processes

3. Human Activities Influence Load and
Retention

4. Impact of Fine Sediment in
River
Light reduction
Bed alteration
Altered hydrodynamics
Oxygen depletion
Scouring
Burial

5. Impact of Fine Sediment loss
from Field
Erosion
Loss of Fertility
Mechanical Difficulties

6. Need a better way to assess and
manage
Fine Sediment

7. Sources of fine sediment
National-scale sediment source
apportionment for England & Wales Relative
contribution of
agriculture to
annual sediment
load
>50%
<50%
Zhang, Collins et al. (2014) Env. Sci. Pol. 42:16-32

8. Insert image here
Insert image here
WQ0128 Extending the evidence
base on the ecological impacts of
fine sediment and developing a
framework for targeting mitigation
of agricultural sediment losses

9. Project structure

10. Impact of Fine Sediment
Assess Extent of Problem
Intrinsic Sediment Yields
Policy Options

11. The concept

12. Yield estimated from lake deposits

13. Psychic 2004 and Targets
Foster, I.D.L., Collins, A.L.,
Naden, P.S., Sear, D.A. &
Jones J.I. (2011) Journal of
Palaeolimnology 45, 287-
306.

14. Impact of Fine Sediment
Review impacts on:
Fish
Invertebrates
Macrophytes
Diatoms

15. Impact of Fine Sediment in
River
Light reduction
Bed alteration
Altered hydrodynamics
Oxygen depletion
Scouring
Burial

16. Impacts via
Suspended Sediment
Deposited Sediment

17. Habitat
Predators
Food

18. Lithophilous (gravel spawning) Fish

19. Kemp et al. (2011) Hydrological Processes
Sediment, Agricultural Calendar and Fish
Reproduction

20. Survival of Atlantic salmon embryos in relation to
% fine sediment
%Survivaltohatch
Kemp et al. (2011) Hydrological Processes

21. Review Papers

22. Reviews of Biological Impacts
– Key Findings
1. Catchment dependency
2. Reach dependency
3. Sediment dependency
4. Taxon dependency
5. Life-stage dependency

23. • Existing evidence base for impacts of fine sediment is
largely correlative
• Failure to elucidate the critical process linkages
between sediment stress and key environmental
parameters/characteristics
Reviews of Biological Impacts
– Key Findings

24. Improved Ecological Evidence
Fish response to sediment stress
– Role of Sediment Oxygen Demand
– New approaches to source apportionment
– Manipulative experiments

25. Fish Experiments
C
C
C
C
C
C
C
C
123510
12 3 510
• Lethal and Sub-lethal Effects
• Identified the Critical Role of Organic Fraction

26. 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100 150 200 250
Brown Trout
Atlantic Salmon
Bank Agriculture Road STW
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Brown Trout
Atlantic Salmon
a
b
c
c d
ee e
MortalityMortality
a)
b) A
B
BCC
Sediment mass added (g wet weight)
Both load and
source important
Sear et al. (submitted)

27. • Extended field evidence and
calibration datasets for Sediment
Intrusion and Dissolved Oxygen
(SIDO)-UK spawning habitat model
• Applied new approaches to source
apportionment – tracing sources of
organic matter
• Developed better understanding of
role of Sediment Oxygen Demand

28. Source fingerprinting
 pasture topsoils
 cultivated topsoils
 damaged road verges
 channel
banks/subsurface
sources
 STWs / point
sources

29. Artificial redd sediment sampling

30. Sediment fingerprinting

31. Sediment fingerprinting

32. Sediment fingerprinting

33. Sediment fingerprinting
• pasture topsoils
– 29±1%
• cultivated topsoils
– 3±1%
• damaged road verges
– 33±1%
• channel banks / subsurface
sources
– 31±1%
• STWs / point sources
– 4±1%

34. Source fingerprinting
 farm yard manures
and slurries
 damaged road verges
 instream decaying
vegetation
 point sources (STWs /
septic tanks)

35. Organics analysis
• shredded material:
– TC / TN
– NIR
– bulk isotopes 13C, 15N
• humic substances:
– fluorescence
– SUVA254
– TOC

36. Sediment Oxygen Demand
Used SIDO-UK to develop a
better understanding of role
of Sediment Oxygen
Demand
Both agricultural and non-
agricultural sediment has the
potential to impact aquatic
ecology.
More organic sediment
derived from point
sources and damaged road
verges resulted in more
pronounced detrimental
effects.
Sear et al. (2014) Hydrological Processes 28: 86-103

37. Improved Ecological Evidence
Invertebrate response to sediment stress
– Correlative field survey
– Manipulative experiments

38. Calibration dataset
• 230 sites sampled for macroinvertebrates & deposited
fine sediment
• across a gradient of modelled sediment pressure
• across a gradient of stream types
• free from STW and urban area inputs
• upstream of lakes & reservoirs
• predominantly agricultural catchments

39. Objectives
• Establish relationship between macroinvertebrate
community and fine sediment pressure at an appropriate
management scale
• Develop a diagnostic biotic index
• Independently test new index

40. Macroinvertebrate sampling
At each site:
– macroinvertebrate sample (RIVPACS protocol)
o record physical features of site
o acquire map-based data

41. Fine sediment sampling
At each site:
o remobilisation stilling well
sample surface drape and embedded fine sediment
from erosional and depositional areas
Processed in the lab for:
 mass of sediment
 organic content
 particle size
Duerdoth et al. (2015) Geomorphology 230: 37–50

42. Duerdoth et al. (2015) Geomorphology 230: 37–50
Fine sediment sampling
Reach scale confidence intervals and reproducibility quantified
0
1
2
3
4
5
0 1 2 3 4 5
site mean log10
surface sediment mass (g m-2
) site mean log10
total sediment mass (g m-2
)
surface drape total
samplelog10
surfacesedimentmass(gm-2
)n-volatile
m-2
)
samplelog10
totalsedimentmass(gm-2
)-volatile
m-2
)
a)
b)
95% Confidence
intervals = ±0.237
4
5
0
1
2
3
4
5
0 1 2 3 4 5
4
5
95% Confidence
intervals = ±0.236
95% Confidence
intervals = ±0.235
95% Confidence
intervals = ±0.227

43. Comparison with visual estimates
of bed composition
surface drape: average
mean substratum size phi
sedimentmassg/m
2
-8 -4 0 4 8
10
0
10
1
10
2
10
3
10
4
10
5
total sediment: average
mean substratum size phi
sedimentmassg/m
2
-8 -4 0 4 8
10
0
10
1
10
2
10
3
10
4
10
5
Visual estimates only explain 50-60% of the variation in fine sediment
mass

44. Analytical Approach
Predicted Sediment Load
Predicted Sediment Retention
Measured Retained Sediment
Measured Sediment Quality
Invertebrate community
range of sediment loadings
within river types

45. Analytical Approach
• Association between variation in the macroinvertebrate
community and the fine sediment stressor gradient
having first factored out that portion of the biological
variation correlated with natural background variation
• Empirical basis for a diagnostic biotic index
• Relationship between modelled agricultural fine
sediment inputs, retentiveness of stream reach and
biological condition of the reach quantified
• Link land-use models to WFD water quality status.

46. Unconfounded
stress gradients

47. Invertebrate response to fine sediment stress comprises two
distinct components
ToFSIsp – index of response to organic component of fine
sediment
oFSIsp – index of response to organic component of fine
sediment
The results of these two indices are then combined
CoFSIsp – combined index of fine sediment stress
Index Development

48. Index response (development sites)
54321
6.5
6.0
5.5
5.0
4.5
4.0
log Fine Sediment Mass (g m-2)
cFSIsp
S 0.348063
R-Sq 56.3%
R-Sq(adj) 56.1%
cFSIsp = 6.553 - 0.5467 logSedMass
CoFSIsp

49. Independent test
26 sites retained from the survey and 57 stream
sites in Wales

50. Independent test
26 sites retained from the survey and 57 stream
sites in Wales

51. Sediment Experiments in Artificial
Stream Channels

52. Jones et al. (2015) Freshwater Biology
Growns et al. (submitted)
Response variables
Turbidity
Deposited Sediment Mass
Oxygen Penetration
Hyporheic Chemistry
Interaction with Flow
Drift
Community Composition
Index Values
Trait Composition
Hyporheic Invertebrates
CONTROL MODERATE HIGH

53. Before After
e)
Control Moderate High
0
0 . 5
1
1 . 5
2
2 . 5
3
3 . 5
4
4 . 5
5
PSIsp
ASPT
cFSIsp
ToFSIsp
Control Moderate High
0
5
1 0
1 5
2 0
2 5
3 0
3 5
Control Moderate High
0
0 . 5
1
1 . 5
2
2 . 5
3
3 . 5
4
4 . 5
5
Control Moderate High
0
1
2
3
4
5
c) d)
f)
CoFSIsp index performs well
PSI index unstable

54. Linking to sediment pressure models
6.05.55.04.54.03.5
6.0
5.5
5.0
4.5
4.0
3.5
Observed cFSIsp
ModelledcFSIsp
(F= 65.5, P < 0.001, R2 = 52.1%).
ModelledCoFSIsp
Observed CoFSIsp

55. Outputs
• Quantified changes in macroinvertebrate
community across a gradient of fine sediment
pressure.
– Identify taxa sensitive and tolerant to fine sediment stress
• Developed and tested a new diagnostic biotic index
• Linked diagnostic index to estimates of sediment
pressure

56. New Modelling Framework
 daily time step
 use of weather data (as opposed to climatic mean)
 explicit representation of pathways (tramlines,
compaction, etc)
 explicit representation of crops and rotations
 drain flow
 connectivity and retention:
 field boundaries types
 particle size distribution and selectivity

57. Conceptual flow pathways in catchments
Preferential flow to
drains
Slow flow to drainsTo groundwater
Plot-scale
runoff
initiation
Field boundary
retention
Landscape
retentionIn-field
retention
MITIGATION

58. Simulation at catchment scale
0
100
200
300
400
500
600
700
800
900
1000
Jul-08 Sep-08 Oct-08 Dec-08 Feb-09 Mar-09
SedimentConc(mg/l)
Predicted
Observed

59. • Downscale catchment scale processes to the channel reach
and redd scales
• use of a hydraulic sediment routing model to link network to
reach scales
In-channel sediment routing
Catchment Reach Redd
> 1 km2
100-50 m
< 1 m
Psychic SIDO-UKRouting

60. Revising estimates of good ecological
status for sediment

61. Use of the modelling toolkit
• catchment-specific
revised sediment targets
• implications for meeting
revised targets of
– mitigation programmes
– climate change
projections for 2020,
2030, 2050, 2080
Mitigation methods for inorganic sediment
Establish cover crops in the autumn
Early harvesting and establishment of crops in the autumn
Cultivate land for crops in spring rather than autumn
Adopt reduced cultivation systems
Cultivate compacted tillage soils
Cultivate and drill across the slope
Leave autumn seedbeds rough
Manage over-winter tramlines
Establish in-field grass buffer strips
Establish riparian buffer strips
Re-site gateways away from high-risk areas

62. Modelling toolkit for managing the
problem
• Ecological status linked to land-use models
to enable managers to explore outcome of
agricultural mitigation options
• Better targeting of mitigation

64. 0
1
2
3
4
5
6
Fast Slow
Clean
Dirty
Numberoftaxa
Flow
Number of taxa
PERMANOVA results
Significant factor % Variance explained
Flow 35
Sediment 14
Interaction with flow

65. Fluorescence composite fingerprints