Siltflux workshop 1: Sediment Research on the Rivers Bandon and Owenabue - Dr. J. 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