Sediment Fluxes Measurement, Impacts, Mitigation and Implications for River Management

EPA Research Programme 2014-2020

Sediment Fluxes – Measurement, Impacts, Mitigation and Implications for River Management in Ireland

(2010-W-LS-4)

EPA Research Synthesis Report

End of Project Report available for download on http://erc.epa.ie/safer/reports

Prepared for the Environmental Protection Agency

by

University College Dublin, University College

Authors:

Professor Michael Bruen

Associate Professor Mary Kelly-Quinn

Dr. John O’Sullivan

Dr. Jonathan Turner

Professor Damian Lawler

Dr. Elizabeth Conroy

Ms. Anna Rymszewicz

ENVIRONMENTAL PROTECTION AGENCY

An Ghníomhaireacht um Chaomhnú Comhshaoil

PO Box 3000, Johnstown Castle, Co.Wexford, Ireland

Telephone: +353 53 916 0600 Fax: +353 53 916 0699

Email: Website: www.epa.ie

9

© Environmental Protection Agency 2017

ACKNOWLEDGEMENTS

This report is published as part of the EPA Research Programme 2014–2020. The programme is financed by the Irish Government. It is administered on behalf of the Department of Communications, Climate Action and the Environment by the EPA, which has the statutory function of co-ordinating and promoting environmental research.

The authors would like to acknowledge the members of the project steering committee, for their guidance and advice at various stages of the project, namely Professor Desmond Walling, Professor John Quinton, Professor Steve Ormerod, Mr. Donal Daly, Dr. Martin McGarrigle, Dr Alice Wemaere, Dr. Martin O’Grady, Dr. Catherine Bradley, Dr. Colin Byrne, Dr. Wayne Trodd, Dr. Marie Archbold.

The project partners also wish to acknowledge the valuable contributions of Dr Sangaralingam Ahilan, John Wallace (IDS Monitoring), Mr. John Hutchings and Ms. Avril Hanbidge.

DISCLAIMER

Although every effort has been made to ensure the accuracy of the material contained in this publication, complete accuracy cannot be guaranteed. Neither the Environmental Protection Agency nor the author(s) accept any responsibility whatsoever for loss or damage occasioned or claimed to have been occasioned, in part or in full, as a consequence of any person acting or refraining from acting, as a result of a matter contained in this publication. All or part of this publication may be reproduced without further permission, provided the source is acknowledged.

The EPA Research Programme addresses the need for research in Ireland to inform policymakers and other stakeholders on a range of questions in relation to environmental protection. These reports are intended as contributions to the necessary debate on the protection of the environment.

EPA RESEARCH PROGRAMME 2014-2020

Published by the Environmental Protection Agency, Ireland

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Details of Project Partners

Professor Michael Bruen (Principal Investigator, Project Coordinator)

School of Civil Engineering, UCD, Dublin 4

Tel.: +35317163212

E-mail:

Associate Professor Mary Kelly-Quinn (Principal Investigator)

School of Biology and Environmental Science, UCD, Belfield, Dublin 4

Tel.: +35317162337

E-mail:

Dr. John O’Sullivan (Principal Investigator)

School of Civil Engineering, UCD, Dublin 4

Tel.: +35317163213

E-mail:

Dr. Jonathan Turner (Principal Investigator)

School of Geography, UCD, Dublin 4

Tel.: +35317168175

E-mail:

Professor Damian Lawler (Principal Investigator)

Centre for Agroecology, Water and Resilience (CAWR),

James Starley Building, Coventry University, Coventry CV1 5FB, England.

E-mail:

Dr. Elizabeth Conroy (Researcher)

School of Biology and Environmental Science, UCD, Belfield, Dublin 4

Tel.: +35317162337

E-mail:

Ms. Anna Rymszewicz (Research)

School of Civil Engineering, UCD, Dublin 4

Tel.: +35317163212

E-mail:

Table of Contents

1 Introduction 10

1.1 Objectives 10

1.2 Methodology 10

1.3 Staffing the project 10

1.4 Workshops 11

1.4.1 Workshop 1: Sediment Fluxes in Irish Rivers 11

1.4.2 Workshop 2: Effects of specific pressures on sediment fluxes 11

1.4.3 Workshop 3: Policy, targets and the reduction of sediment in Irish Rivers. 11

1.5 Organisation of Reporting. 12

1.5.1 Project Documents and datasets 12

2 Site selection, instrumentation and operational methods 13

2.1 Catchment and site selection criteria 13

2.1.1 Chosen SILTFLUX monitoring catchments 13

2.2 Selecting field sites for instrumentation 14

2.3 Description of chosen instrumental approach and operational methods 15

2.3.1 Background 15

2.3.2 Measuring turbidity and SSC 15

2.3.3 Estimating suspended sediment flux 15

3 Instrument evaluation – laboratory/tank and field tests 18

3.1 Introduction 18

3.2 Laboratory Testing 18

3.3 Field Testing 18

3.4 Discussion 20

4 Field data: processing, presentation, analyses and quality control 21

4.1 Introduction 21

4.2 Time Series of Water Turbidity 22

4.3 Discharge data 24

4.4 Issues Encountered in Collecting Field Data 24

4.5 Data quality assurance and control 24

4.6 Time Series of Suspended Sediment Concentrations 25

4.7 Sediment Flux Data 26

5 Modelling annual suspended sediment yields 31

5.1 Introduction 31

5.2 Purpose of analysis 31

5.3 Annual load data, catchments and sources 31

5.4 Potential predictor variables with national availability. 34

5.4.1 Area-specific suspended sediment yield (SSY) multiple regression model 36

5.4.2 Absolute suspended sediment yield (SY) multiple regression model 38

5.4.3 Validation of SY model 41

5.5 Extension of models with additional predictors 42

5.6 Discussion 45

6 Biological Investigations 47

6.1 Evaluation of methods to estimate levels of deposited sediment. 47

6.2 Impact of a localised source (i.e. cattle access points) of sediment on Ecological Water Quality in Streams 47

6.3 Relationship between Biotic and Sediment Metrics 49

6.4 Land-use Effects on Benthic Macroinvertebrate Communities 50

6.5 Responses of Selected Macroinvertebrate Taxa to Burial by Sediment 56

7 Measures for reduction in suspended sediment impacts 58

7.1 Introduction 58

7.1.1 Riparian and in-stream options 61

8 What has been learned about sediment fluxes in Irish Rivers and its impact – on Policy Formulation 65

8.1 Monitoring & Measuring 65

8.1.1 Instrument Differences 65

8.1.2 Instrument Noise 65

8.1.3 Sediment Particle Size Influences Turbidity Measurements 65

8.1.4 Good Turbidity-Suspended Sediment Concentration Relationships can be Established 65

8.1.5 Calibrated Estimates of Suspended Sediment Concentration can be used to Estimate Suspended Sediment Flux and Loads 65

8.1.6 Turbidity should not be used as a Water Quality Metric in a Regulatory Framework 65

8.1.7 Need for Instrument Meta-Data 66

8.1.8 Maintenance and Resilience 66

8.2 Data Quality 66

8.2.1 Turbidity Data may contain Spurious Trends and Data Peaks 66

8.2.2 Real-Time Data Collection Systems can assist in the Timely Response to Data Collection Problems 66

8.2.3 Secondary Datasets can be used to assist in Data Quality Assessment 66

8.3 Flux and Yield Estimation 66

8.3.1 Database 66

8.3.2 Need for Long-Term Sediment Monitoring in Catchments 67

8.3.3 Estimating Sediment Yields using Regression Models 67

8.3.4 Towards a National Inventory of Sediment Yields and the Setting of Environmental Quality Standards (EQS) for Sediment 67

8.4 Impacts on Freshwater Biology 67

8.4.1 Sediment Exceedance Duration Curves for Suspended Sediment 67

8.4.2 Importance of Deposited Sediment 67

8.4.3 Standards for Deposited Sediment 67

8.4.4 Burial can be a Factor in the Impact of Deposited Sediment. 68

8.4.5 Metrics should be based on Sediment Sensitive Taxa 68

8.4.6 Thresholds based on Sediment Cover require More Research 68

8.4.7 Deposited Sediment Amounts can be Assessed Visually 68

8.4.8 Mid-Channel Organisms Most Affected by Cattle Access Points 68

8.4.9 Cattle Access Points Impact Greater on Higher Status Rivers 68

8.4.10 Seasonal Effects on the Impact of Cattle Access Points 68

8.4.11 Outdoor Overwintering of Cattle 68

8.4.12 Challenge of Disentangling Sediment Effects from those of Nutrients and Organic Matter 69

8.4.13 Different Responses to Scales of Pressures 69

8.4.14 Pasture Impacts 69

8.4.15 Tillage Impacts Less Consistent 69

8.5 Implications for Management of Suspended Sediment in Rivers 69

8.5.1 Scale of Problem 69

8.5.2 Management Steps for Sensitive Habitats 70

9 Priority Areas for Immediate Action 71

9.1 Use of Turbidity 71

9.2 Further Challenges in Estimating Sediment Loads 71

9.2.1 Investigate the Sediment Yields from Rivers under Different Land-uses 71

9.2.2 Investigate the Sediment Yields from Rivers Subjected to Arterial Drainage 71

9.2.3 Investigate Sediment Yields and Dynamics in Lake Areas 71

9.2.4 Investigate How to Extend this Study to Larger Catchments 71

9.2.5 Investigate and Model Hysteresis in the Suspended Sediment Dynamics in Rivers 71

9.2.6 National Suspended Sediment Risk Map 72

9.2.7 Suspended and Deposited Fine Sediment Relationships 72

9.3 Biology 72

9.3.1 Scale of Future Studies 72

9.3.2 Visual Estimates of Fine Sediment Cover Should be Made Routinely 72

9.3.3 Thresholds for Impacts from Deposited Sediment Should be Investigated 72

9.3.4 New Sediment Specific Biological Metrics Needed (Disentanglement) 72

9.3.5 Interim Suggestion 73

9.3.6 Long-Term Datasets Needed 73

9.3.7 Outdoor Over-Wintering of Cattle 73

9.4 Priority Actions 73

9.4.1 Initiate Long-Term Monitoring of Turbidity and Suspended Sediment Fluxes 73

9.4.2 Initiate Suspended Sediment Monitoring Across a Broader Range of Land-use and Catchment Conditions 73

9.4.3 Set Standards for Suspended Sediment Concentrations in Irish Catchments 73

9.4.4 Ensure Collaboration of Agencies and Stakeholders Collecting Suspended Sediment Data in Ireland 74

9.4.5 Establish Standard Operating Procedures for the Monitoring of Suspended Sediment in Rivers 74

9.4.6 Establish Standard Protocols for Assessment of Deposited Sediment in Rivers 74

9.4.7 Establish a Threshold for Deposited Sediment in Rivers 74

10 References 75

List of Tables

Table 21 Sites for suspended sediment concentration measurements (ISCO water samplers and in-situ turbidity sensors)). 16

Table 22 Sites for in-situ turbidity sensors (OPW and Siltflux). 17

Table 41 Summary of data collected at monitoring sites during the SILTFLUX project 21

Table 42 Turbidity (NTU) – Suspended Sediment Concentration (mg/L) equations 23

Table 43 Summary of annual rainfall, discharge, SSC and sediment yield data 27

Table 51 SSY data for Irish catchments, catchment size (A), study period and data source. 32

Table 52 Catchment characteristics obtained for each study catchment 34

Table 53 Catchment hydrological descriptors specific for the study period derived for each catchment 36

Table 54 Six parameter SSY model summary 37

Table 55 Six parameter SY model output 39

Table 56 Measure of model fit between Calibration and validation datasets 42

Table 57 Alternative six-parameter SY model output, with associated significance levels of each parameter and model fit to log transformed data. 43

Table 58 Measures of alternative SY model fit between calibration and validation datasets 44

Table 61 SIMPER analysis identifying the main taxa that made the largest contributions in community structure in autumn 53

Table 62 Results of non-parametric multiple regression of pasture community structure 54

Table 63 SIMPER analysis identifying the main taxa that made the largest contributions in community structure for patch and reach-scale tillage sites 54

Table 64 Results of non-parametric multiple regression of tillage community structure 55

Table 71 On farm options for reducing sediment export 59

Table 72 Stream bank/riparian methods for sediment reduction 61

List of Figures

Figure 21 The experimental design used for locating monitoring sites 13

Figure 22 Location of SILTFLUX project and OPW catchments. 14

Figure 23 Methodology for estimating sediment fluxes 17

Figure 41 River Slaney downstream: turbidity and corresponding SSCs 22

Figure 42 River Slaney downstream: Turbidity-SSC relationship 24

Figure 43 River Slaney downstream: SSC with corresponding discharge, showing measured SSCs from water samples 25

Figure 44 River Slaney downstream: Suspended sediment flux and discharge 26

Figure 45 Frequency-duration plots of suspended sediment concentration exceedance with time for the study sites. (A) Camlin (2014), (B) Glyde (2014 - 2015), (C) Clodiagh U/S (2014), (D) Clodiagh D/S (2015), (E) Urrin (2014, (F) Slaney D/S (2012 - 2014), (G) Clare U 28

Figure 46 Concentration-duration-frequency (CDF) plots for the study sites: (A) Camlin (2014), (B) Glyde (2015), (C) Clodiagh U/S (2014), (D) Clodiagh D/S (2015), (E) Urrin (2014) and (F) Slaney D/S (2014) for the events that exceed 25 mg L-1, 50 mg L-1 and 150 mg L-1. 29

Figure 47 Percentage distribution of sediment load for each month of the year for the study sites: (a) Camlin, (b) Glyde, (c) Clodiagh U/S, (d) Clodiagh D/S, (e) Urrin, (f) Slaney D/S, (g) Clare U/S (2011 – 2012), (h) Clare U/S (2013-2014), (i) Clare D/S 30

Figure 51 Locations of study catchments and sources of data. 32

Figure 52 SSY model fit showing scatter plot between measured and modelled SSY. 38

Figure 53 SY model fit showing scatter plot between measured and modelled SY. 40

Figure 54 Six parameter model fit - scatter plot between measured and modelled SY 40

Figure 55 Calibration and validation scatter plots for SY 41

Figure 56 Calibration and validation of SY model with datasets reversed 42

Figure 57 Fitting of alternative six parameter equation with Q5 as a predictor 44

Figure 58 Scatter plots for alternative SY for both calibration (A) and validation (B) data. 45

Figure 59 Calibration (B) and validation (A) of alternative SY model with datasets reversed 45

Figure 61 Location of the eight study rivers catchments, colour codes for water quality upstream of the cattle access points 48

Figure 62 Mean (± standard error) abundance of Heptageniidae (Hept.) drifting 50

1  Introduction

1.1  Objectives

The SILTFLUX project addressed three major objectives:

(i)  increase knowledge and understanding of silt flux in Irish rivers to help set standards for suspended solids for the protection of sensitive catchments;

(ii)  assess the benefits of silt reduction that mitigation measures can achieve, differentiating between the effects of fine and coarse sediments;

(iii)  understand the relationship between suspended silt concentration/flux, deposited silt and ecological impacts in different river typologies and under variable land-use.

1.2  Methodology

The project started with a review of knowledge of sediment fluxes, their measurement and, later, of measures for reducing or mitigating their impact. In parallel, the project selected study catchments in which sediment flux data and biological information would be collected. The data provided information on the factors influencing sediment fluxes in Irish rivers under a range of conditions and on their biological impact. The catchment studies were augmented with laboratory investigations of specific topics both relating to turbidity measurement and to the biological impact. The data sets collected by the project, together with other published data, provided a basis for establishing a methodology for generating predictive equations relating annual sediment yield to catchment and climate characteristics. All of the information and results generated by the project support a wide range of recommendations, both for how this information can inform river management policy, and also what further research is required.

1.3  Staffing the project

SILTFLUX involved two main partner Institutions, University College Dublin (UCD) and University of Birmingham, (UB). However, many other Institutions contributed during the course of the project, including Cork Institute of Technology (CIT), the Marine Institute (MI). Dr. Martin O’Grady was an advisor to the project, particularly in its initial phases. The main researchers involved were