8. Flow and Form
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This presentation was given as part of the EPA-funded Catchment Science and Management Course focusing on Integrated Catchment Management, held in June 2015. This course was delivered by RPS Consultants. If you have any queries or comments, or wish to use the material in this presentation, please contact catchments@epa.ie It is increasingly being recognised internationally that integrated catchment management (ICM) is a useful organising framework for tackling the ongoing challenge of balancing sustainable use and development of our natural resource, against achieving environmental goals. The basic principles of ICM (Williams, 2012) are to: • Take a holistic and integrated approach to the management of land, biodiversity, water and community resources at the water catchment scale; • Involve communities in planning and managing their landscapes; and • Find a balance between resource use and resource conservation ICM is now well established in Australia, New Zealand, and the United States. In Europe the ICM approach has been proposed as being required to achieve effective water and catchment management, and is the approach being promoted by DEFRA for the UK, where it is called the “Catchment Based Approach” (CaBA). The principles and methodologies behind ICM sit well within the context of the Water Framework Directive with its aims and objectives for good water quality, sustainable development and public participation in water resource management. In Ireland it is proposed that the ICM approach will underlie the work and philosophy in developing and implementing future River Basin Management Plans.
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8. Flow and Form
- 2. River Flow and Form Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments 1. What Can River Flow and Form Tell Us? 2. Flow – What Data is Available? 3. The Hydrograph 4. Base Flow Index 5. What Determines Hydrograph Shape? 6. Catchment Descriptors 7. Hydrograph Examples including the Nuenna 8. Channel Form – Expectation vs what you see on the Ground 9. Recording Disturbance / Departure from Naturalness 10.Land Use (Indirect) Pressures 11.Direct Pressures
- 3. What can River Flow data tell us? • Use in combination with nutrient concentrations to calculate pollutant load • Establish flow duration curves and estimate low flows for assimilative capacity calculations • Flood flows have power to lift and transport high sediment loads Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments
- 4. What can River Form tell us? • Departure from reference condition • Indication of pressures – a river’s form is not what you expect to see for the type of channel and where it is in the overall catchment Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments
- 5. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Flow – what data is available? Hydrometric Data from Gauging Stations across Ireland – 216 with water level and flow data that has some degree of confidence at higher flows. • Water level is recorded • Spot gaugings taken to record water level and flow • Rating relationship developed
- 6. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments EPA maintain the Register of Hydrometric Stations in Ireland EPA Hydronet website http://hydronet.epa.ie • Download average flow data for Local Authority gauges • Request continuous water level and flow data and annual maximum series Flow – what data is available?
- 7. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments The Office of Public Works – approx 500 gauging stations with varying data quality – www.opw.ie/hydro • Download average flow and level data OPW gauges • Download annual maximum series • Continually updated by OPW Hydrometric Section Flow – what data is available?
- 8. The Office of Public Works - FLOOD STUDIES UPDATE – WEB PORTAL opw.hydronet.com • Substantial update of the Flood Studies Report (NERC, 1975), that provided methodologies for flood estimation in Ireland and the United Kingdom. • Solely based on Irish Data. Key outputs for Catchment Management: • Review of hydrometric stations and creation of database of the 216 most reliable in terms of flow data at higher flows. • GIS based calculation of Physical Catchment Descriptors along every river in Ireland – these datasets are key Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Flow – what data is available?
- 9. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Flow – what data is available? • Publicly available – launched November 2014 • Provides links to other hydrometric websites • Excellent source of spatial datasets on a national basis
- 10. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Flow – what data is available? Hydrometric Stations (216 ) •Annual maximum data (high flows) •Continuous water level and flow series Spatial Layers useful for catchment management •Location of hydrometric stations •Ungauged catchment descriptors (133846 locations) •Gauged (216) and Ungauged catchment boundaries •Rivers •Lakes •Hydrometric areas •Cities and Towns •River Basin Districts •Townlands •Depth Duration Frequency grid points for rainfall All downloadable from the FSU WEB Portal
- 11. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Flow – what data is available? www.waterlevel.ie
- 12. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments The Hydrograph • Hydrograph is the sum of all water discharging to the river • Pathways to the river: 1. Overland Flow: Surface runoff & flows in land drains 2. Interflow: seepage through soils and subsoils 3. Shallow Groundwater Flow: through weathered rock 4. Deep Groundwater Flow: Groundwater flow beneath the water table that interacts with the surface water system 5. Discrete Fault or Conduit Flow • Base Flow Index (BFI) = (Qi+Qg) / Q (0 to 1) (Deakin 2012) BFI is a good indicator of hydrological response
- 13. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Base Flow Index • The FSU WEB Portal can provide estimated BFI data for all ungauged catchments • Estimated using combination of nearby gauge data and soil / aquifer data • BFIsoil index is a useful summary of the hydrological behaviour of rivers at a catchment scale (FSU WP 5.2) • Ratio between 0 and 1 • Lower values indicate greater contribution from overland flow i.e. Quicker response, higher potential for sediment transfer
- 14. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 02/11 /2009 04/11 /200906/11 /2009 08/11 /2009 10/11 /200912/11 /2009 14/11 /200916/11 /2009 18/11 /2009 20/11 /200922/11 /2009 24/11 /2009 26/11 /200928/11 /2009 30/11 /2009 02/12 /200904/12 /2009 06/12 /2009 08/12 /200910/12 /2009 12/12 /2009 14/12 /200916/12 /2009 25017 26007 What determines hydrograph shape? Meteorological Characteristics– the driver Generally precipitation dominates the Rising Limb Catchment descriptors control the response Recession Limb is determined by catchment characteristics Baseflow Gauging Station No.
- 15. Catchment Descriptors • Shape of the drainage basin (catchment) • Drainage density • Slope Influences the time taken for water from the remote parts of the catchment to arrive at the outlet Area C1 Area C2 Area C1 Area C2
- 16. Catchment Descriptors • Geology (permeable/impermeable) • Soil type (permeable, deep, shallow etc) • Landuse (urban, forest, agriculture) • Presence of bogs, turloughs, lakes and reservoirs • Artificial drainage schemes Control surface water runoff, shape of recession limb Part of BFIsoil
- 17. Channel and floodplain characteristics - cross-section shape - channel roughness - online reservoirs - floodplain storage Control conveyance (in-channel flow)
- 18. Assume that only one factor changes Amount of storm rainfall increases Duration of storm increases Storm changes from complete coverage of the catchment to only partial coverage Rate of snowmelt increases Catchment size increases Catchment slope changes from steep to flat Landuse changes from rural to urban Catchment is wet prior to the storm Fields ploughed along the contours are ploughed across the contours Geology changes from clay to limestone Flood peak Increases Decreases Decreases Increases Increases Decreases Increases Increases Increases Decreases
- 19. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Flow(cumecs) Time Catchment 'X' - Reduced Vegetation Catchment 'X' Reduction in Time to Peak Higher Peak Flow Example: Overgrazing
- 20. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Catchment Y Attenuation Catchment Y No Attenuation Lower Peak Flow Longer recession limb Example: Flow attenuation
- 21. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Nuenna Catchment AREA: 92 km2 SAAR: 859 mm URBAN EXTENT: 0.2% DRAINAGE DENSITY: 0.83 km/km2 SLOPE: 13.2m/km FARL: 1 BFIsoil: 0.57 Use FSU WEB Portal to get catchment descriptors and estimate: • Index Flow (Annual maximum - 15 m3/s) • Flood Frequencies • Hydrograph Shape This can be done at any of the 100 nodes points shown in the catchment
- 22. Nuenna Catchment Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 Flow(cumecs) Time (Hours) Flow (m3/s) – 2 year return period
- 23. Build Partnership Characterise Watershed Set Goals and Identify Solutions Design Implementation Program Implement Program Make Progress Make Adjustments Improve Plan•Largely dictated by topography •Ireland has a relatively flat landscape surrounded by coastal hills. •Channels vary from steep fast flowing upland narrow streams to wide, shallow and sluggish lowland meandering rivers Channel Form Channels and Challenges O’Grady, 2006
- 24. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Channel Forms you Expect to See • High gradient streams with high transport capacity • Fast turbulent flow • Flat sheets of bedrock or large boulders and cobbles • May feature waterfalls and plunge pools • Banks formed from bedrock or large boulders – erosion resistant except from very high discharges • Mosses, lichens, algae Upper Reaches of the Catchment
- 25. Mid Catchment • Moderate gradient channels • Substrate of mostly pebble and gravels with patches of sand • Flow types made up of riffle sections interspersed with pools and glides • Bank stability dependent on erodibility of bank material and vegetation cover • Some macrophytes at channel margins Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Channel Forms you Expect to See
- 26. Lower Catchment • Low to no gradient • Smooth Flow • Low velocities • Fine Substrates • Macrophytes • Stable banks • Mid channel islands Channel Forms you Expect to See Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments
- 27. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Comparing Expectation with What you See on the Ground Expected conditions for an upper - mid catchment river in West of Ireland • Low BFIsoil index – mostly overland flow, flashy response • Stable banks • Pebble and cobble substrate, some large boulders
- 28. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Comparing Expectation with What you See on the Ground What is causing this departure from expectations? Unstable banks - Excessive Erosion Excessive fine sands and silts
- 29. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Comparing Expectation with What you See on the Ground Expected conditions for a lowland meandering river in the Midlands • High BFIsoil index – high groundwater contribution, slower response wide hydrograph • Connected to flood plain • Low depth to width ratio • Fine substrate • Meanders with erosion on outside and deposition on inside • Mid channel islands
- 30. On Site: • Channelised • Straight uniform trapezoidal channel • Disconnected from flood plain • High depth to width ratio • Excessive sediment in channel • Uniform flow • Bare exposed banks Comparing Expectation with What you See on the Ground Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments
- 31. Recording Disturbance / Departure from Naturalness • Channel form and flow types – is river on its natural course? Variety of depths and water velocity where expected? Presence of natural features? • Channel vegetation – vegetation in channel as expected – habitat and organic debris • Substrate condition – depends on stream type and geology, heterogeneity of substrate present, how embedded are coarse particles by fines, quality and cleanliness, alterations. WHAT PRESSURES ARE CAUSING THIS DEPARTURE FROM NATURALNESS? Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments
- 32. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Land Use (Indirect) Pressures Source: Land Use Activities e.g. Forestry Grazing, peat cutting Pathway: Overland Flow – transfer of excess sediment load Receptor: River – excessive sediment load impacting ecology
- 33. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Direct Pressures Cattle poaching Modified channel Dam causing barrier to upstream fish migration
- 34. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Direct pressures Modified Banks Cattle poaching Barriers to Migration
- 35. Build Partnership Create an ICM Vision Characterise the Catchment Undertake further characterisation Identify & Evaluate Possible Management Strategies Design an Implementation Programme Implement the River Basin Management Plan Measure Progress and Make Adjustments Identifying Pressures by looking at channel flow and form can help to focus fieldwork investigations and identify the measures needed to address the issues