Aerial image of the Ulster Blackwater, an EREP study catchment.

Environmental River Enhancement Programme | EREP

The aim of the Environmental River Enhancement Programme (EREP) is to investigate the status of habitats and species, primarily fish, in drained catchments. We aim to develop and implement channel maintenance and management practices and to advise mitigation measures that are appropriate to the channel type, taking hydromorphology into account.

Measuring river flow using acoustic Doppler current profiling on the River Liffey.

Historical drainage and flood relief works

Natural channels contain a variety of physical habitats, all interacting together to create ecological diversity. In the 1940s, extensive arterial drainage works were undertaken by the Office of Public Works (OPW) to reduce flooding and improve land drainage. These works were carried out on whole river catchments and involved substantial physical changes to the channels.

Surveying the Stonyford River.

Destruction of natural processes

The deepening, widening and straightening of river channels completely altered their natural beds and flow patterns and destroyed important habitats. Though positive for land drainage, these changes dramatically impacted the ecology of our rivers, leaving many with unnaturally high, steep banks and cut off from their natural floodplains.

Preparing for boat electrofishing.

High maintenance and further impact

Expensive, on-going channel maintenance is required by law to retain the flood-management and land-drainage gains of the original drainage works. Maintenance involves the removing obstructions within the channel, such as fine sediment deposits, vegetation and fallen trees, with the maintenance process itself posing an additional risk to the river.

Stonyford 2020 after restoration works.

Guiding practice & more sustainable solutions

In 1990, the Office of Public Works (OPW) began a study with Inland Fisheries Ireland, called the Environmental Drainage Maintenance Programme (EDM), to examine the effects of on-going channel maintenance and cleaning. We wanted to see if maintenance could be done in a way that was less damaging and even provide environmental benefits to the channel. This programme carried out scientific studies and identified practical ideas that could be included into everyday work by OPW’s channel maintenance crews. A guidance plan for environmental maintenance procedures was produced, with training provided to OPW staff. Some of these measures are now standard practice in their operations.

In 2008, the EDM was replaced by a new project, the Environmental River Enhancement Programme (EREP). This work built on the previous programme and implemented more substantial instream and bank-side works to improve the river habitats. We focused on two main components, the transportation of building materials onto a site and robust implementation of the OPW’s original guidance plan. Annual audits were undertaken of OPW machine crews to assess their progress. In addition, a series of scientific studies were undertaken, covering a range of species and topics in drained river channels.

The EREP is currently focused on scientific studies and data collection. This includes:

  • Catchment-wide studies on fish, habitat and barriers in areas where the OPW have drainage operations.
  • Development of a long-term monitoring programme at locations where drainage works have taken place. Repeat surveying helps us to assess recovery and improvements.
  • Opportunistic investigations and scientific experiments to explore other new avenues, such as gravel trap removal, reconnection of cut-off channels and fish passage issues.
  • Implementing and monitoring in-stream works using “soft materials”. This includes the use of trees to influence flow and bank protection structures to restore natural erosion and deposition. 

This programme continues to work closely with the OPW and encourages best practices, while trialing new experimental projects. We strive to develop new protocols and methods for undertaking catchment-wide surveys and long-term monitoring.

Measuring a salmon parr.
Infographic of the EREP project 2012 to 2022