Presentation given by Joe Harrington, Cork Institute of Technology,at the workshop on Sediment Fluxes in Irish Rivers (Siltflux Workshop) = 28/10/14, UCD, Dublin 4
Sediment Research on the Rivers Bandon and Owenabue, Ireland - Joe Harrington
1. Sediment Research on the Rivers Bandon and
Owenabue, Ireland
Dr. J. Harrington
Cork Institute of Technology
Presented at SILTFLUX Workshop, UCD
28th October 2014
2. Outline of Presentation
• Introduction
• Study Catchments and Characteristics
• Data Collection Programme
• Sediment Fluxes and Yields
• Storm Based Events
• Nutrient Transport
3. Introduction
• Sediment Research has been underway at Cork Institute of
Technology for the past decade
• The focus has been on the nearby Rivers Bandon and
Owenabue
• The research work has studied suspended sediment
concentrations and loadings based on a field sampling and
continuous turbidity monitoring programme
8. Parameter Detail Parameter Detail
River Details: Station:
Catchment Bandon
Station Catchment
Area
424 km-2
Catchment Area 608 km-2 Length to Station 52.55 km
River Length 77 km Station Type Data Logger & Turbidity Probe
Altitude at source 320m OD Body Responsible Office of Public Works & CIT
Average Slope 4.16 m km-1 (from OS maps) Co-ordinates 51.74N, -8.68W
Average Flow Rate 15 m³ s-1 Staff Gauge Zero 6.94 m O.D.
Annual Average Rainfall 1207 mm/year (Cork Airport) Records Available 1975 - Date
Land Use Tillage, pasture, forestry, urban Turbidity Data 2010 - date
River Bandon – Summary Data
9. River Bandon Catchment – Some Information
• Relatively large sized catchment in an Irish context (608 km2)
• Primarily agricultural 94% (tillage and pasture)
• Prone to flooding
• Distinguished by engineered works on stretches
• Features a number of special areas of conservation (SAC)
• Exhibits a range of levels of water quality
• Features both suspended and bed load transport
• Dredging undertaken through the town of Bandon (post-2010)
• River improvement works proposed for 2015 and 2016
• River discharge to Kinsale Estuary
10. River Bandon – Data Collection
Manual Sampling Programme
At the Curranure Hydrometric Station
Samples tested for:
Suspended Sediment Concentration (SSC)
since 2004 and turbidity since 2007
Range of Nutrient Parameters
- Nov. 2009 to 2012
Additional suspended sediment and bed
sediment samples have been collected at a
number of locations along the river since
April 2012.
Automatic sediment sampler installed in
September 2014
Continuous Monitoring Programme
Turbidity data at 15 minute resolution
(February 2010 – date)
Campbell Scientific OBS 3+ probe
River stage/flow rate data at 15 minute
resolution
12. Parameter Detail Parameter Detail
River Details: Station:
Sub-Catchment (of the
Lee)
Owenabue
Station Catchment
Area
103 km-2
Sub-Catchment Area 105 km-2 Length to Station 19.05 km
River Length 22.71 km Station Type Data Logger & Turbidity Probe
Altitude at source 110m OD Body Responsible Office of Public Works & CIT
Average Slope 6.34 m km-1 (from OS maps) Co-ordinates 51.82N, -8.42W
Average Flow Rate 2.294 m³ s-1 Staff Gauge Zero 11.29 m O.D.
Annual Average Rainfall 1207 mm/year (Cork Airport)
Water Level Records
Available
1956 - Date
Land Use Tillage, pasture, forestry, urban Turbidity Data 2009 - Date
River Owenabue – Summary Data
13. River Owenabue – Some Information
• A smaller scale catchment (105 km2)
• Primarily agricultural (97%) - tillage and pasture
• Moderate to poor water quality status
• Catchment hill slopes are quite steep with quick response to rainfall
• River discharge to Cork Harbour via town of Carrigaline
14. River Owenabue – Data Collection
Q = 13.6 m3 s-1 (Peak Flow of Event)
SSC = 123 mg L-1 (4 hours after peak)
Manual Sampling Programme
At the Ballea Bridge Upper Station
Samples tested for:
Suspended Sediment Concentration (SSC) since
2004 and turbidity since 2007
- to 2012
Range of Nutrient Parameters
- 2007 to 2012
Continuous Monitoring Programme
Turbidity data at 15 minute resolution
(Sept. 2009 – date)
Campbell Scientific OBS 3+ probe
River stage/flow rate data at 15 minute
resolution
16. Sediment Flux Analysis
Ls= 𝑸 𝒕 𝑺𝑺𝑪 𝒕 dt
t2
t1
where
Ls = load over a time period (t2 - t1),
Qt = flow rate at time t
SSCt = suspended sediment concentration at time t
Ref: Harrington, S.T., Harrington, J.R., ‘An assessment of the suspended
sediment rating curve approach for load estimation on the Rivers
Bandon and Owenabue, Ireland’, Geomorphology 185 (2013) 27-38.
18. Suspended Sediment Flux and Yield
SS Flux (tonnes/year) SS Yield (tonnes/ha/year)
Feb. ’10 –
Feb. 11
Feb. ’10 –
Feb. 12
Feb. ’10 – Feb.
11
Feb. ’10 –
Feb. 12
River Bandon 6012 4128 0.142 0.097
SS Flux (tonnes/year) SS Yield (tonnes/ha/year)
Sept. ’09 –
Sept. 10
Sept. ’09 –
Sept. 10
Sept. ’09 –
Sept. 11
Sept. ’09 –
Sept. 11
River
Owenabue
2636 1822 0.256 0.177
19. Storm Based Events
• Disproportionate delivery of suspended sediment flux on
infrequent high flow events
• Approximately 75% of the suspended sediment load is
transported on flow rates above the 10% exceedance level.
• Storm events identified and analysed
• Suspended sediment rating curves analysed (high degree of
variability found in the Q-SSC relationship)
23. Nutrient Transport
• Dissolved and particulate nutrient behaviour investigated
• Wide variability in nutrient concentrations
• Discharge and SSC influence concentrations
• Turbidity found to be a suitable surrogate for some phosphorous
parameters (TP and PP) but nitrogen parameters were not well correlated
Ref: Harrington, S. T. and Harrington, J. R.: Dissolved and particulate nutrient
transport dynamics of a small Irish catchment: the River Owenabue, Hydrol.
Earth Syst. Sci., 18, 2191-2200, doi:10.5194/hess-18-2191-2014, 2014.
24. Acknowledgements
• Funding Sources
IOTI Technological Sector Research Programme
Office of Public Works
Byrne Looby PHMcCarthy
• River Data
Office of Public Works
EPA
• Postgraduate Research Team
Sean Harrington, James Hickey, John Gamble, Kevin Motherway,
John Clancy