Office of Public Works Arterial Drainage Maintenance An Environmental Approach Richard Dooley, Engineer Gr. 1, Galway, Ireland. Acknowledgements Thanks to Nathy Gilligan, Environment Section OPW, John Murphy, Regional Engineer, West Region and Dr. Jimmy King of the Central Fisheries Board for their assistance.
OPW role in Arterial Drainage Maintenance OPW are in existence for 150 years. Drainage and flood relief works commenced under the 1842 Drainage Act. Body through which Central Government exercises its statutory responsibilities in respect of: (a) River Drainage (b) Flood Relief
1945 Arterial Drainage Act Investigation & preparation on whole catchment basis. Some sixty catchments identified. Thirty four catchment schemes completed together with four Estuarine Embankment Schemes. 260,000 Hectares of land benefited. Statutory maintenance responsibility.
1995 Amendment to the 1945 Act In response to major Urban Flooding in 1994/1995. Empowered the Commissioners to carry out drainage schemes for the alleviation of localised flooding. Ten schemes have been carried out, three others at works stage.
Maintenance Data 11,504 Km of Channel (90% < 3metre base width) 733Km of Embankment 18,500 Bridges Sluices, Pumping Stations and Barrages 2000 Km of channel maintained annually
Resources on Maintenance A trained permanent direct labour workforce of over 300. Engineering expertise. An annual budget of over 13 Million. A fleet of 80 dedicated excavators. Jeeps, Low Loaders, Tractors, Trucks and ancillary equipment.
Annual Maintenance Programme Prepared by each Region towards the end of the preceding year. Programme compiled for individual machine units - detailed by channel. Programme includes inspections, repairs/replacement of structures & embankments.
Traditional Channel Maintenance Removal debris, silt deposits, in channel vegetation and clearing of bank slopes. Restoration of the design trapezoidal section. Input sought from the Regional Fisheries Boards and account taken of their concerns.
Traditional Channel Maintenance
Changes in Drainage Maintenance Use of modern fleet of low ground pressure hydraulic machinery. Increased liaison with Regional Fisheries Boards & Dúchas the Heritage Service. Central Fisheries Board Experimental Drainage Maintenance Programme Commenced in the East Region in 1990 Extended to all Regions in 1997
Consultations with Regional Fisheries Boards Regional Fisheries Boards Consultation at all levels - Formal Meeting On more sensitive schemes bi-monthly meetings are held Timing of entry onto spawning, nursery and angling channels.
Channel redefined Stone weirs reconstructed Fishery enhancement works
Consultations with Dúchas - The Heritage Service Programmes copied to Regional Managers Formal meetings arranged by OPW Consultation and notifications to District Conservation officers when entering on or directly impinging upon National Heritage Areas (NHA s) Special Areas of Conservation (SAC s) Special Protection Areas (SPA s)
Experimental Drainage Maintenance Programme Fully funded by the OPW - drawing on the expertise of Central Fisheries Board Staff Experimental environmentally friendly approaches were assessed. Training Course in Environmentally Sensitive Channel Maintenance was developed jointly by the OPW & CFB - Training has been provided for all outdoor staff.
Central Fisheries Board - EDM Programme Ten key environmentally friendly initiatives identified on channel maintenance Culminating in the identification of changes in practice
1. Working on one bank only
2. Restrict maintenance to channel Remove Retain and top berm Retain marginal grass
3. Deposit spoil on Bank Full, not Bank Slope
4. Selective Vegetation Removal Canary grass Phalaris Bullrush Scirpus
5. Leave sections untouched
6. Management of Trees
7. Replace boulders - to break up flow and create fish lies
No. of redds 8. Loosen spawning Gravels 20 18 16 14 12 10 8 6 4 2 0 Control Experimental 1990/91 1991/92 1992/93 Years
9. Manage berms - two stage channel
10. Excavate Pools Too wide & shallow Pool excavated
Further initiatives Draft protocols have been introduced to address the level and format of our interactions with: Dúchas Regional Fisheries Boards Central Fisheries Board Ensuring continued compliance with existing Irish and EU Environmental Legislation. GIS presently being developed as primary data management tool.
Environmental Channel Maintenance - The future Environmental guidance document for machine operatives. Monitoring of level of compliance with environmental methods adopted from the Experimental stage. Channel categorisation by Habitat.
OBJECTIVE Arterial Drainage with improved habitat & wildlife.