Step III - Project Construction

Many factors will influence your choice between design options when you come to constructing a river restoration scheme (Table 3). Bear in mind that any designs are site-specific and depend on local circumstances. These include:
 

Table 3 Important considerations prior to, and during construction

Adjacent land use
 
The river restoration scheme may be just part of a larger development area that will have detailed development proposals or a masterplan. Therefore ‘looking’ upstream and downstream and the surrounding area will influence your design. All elements of masterplanning, including water access and transport routes, wider wildlife corridors, and sustainable drainage systems, should be considered in parallel with the river and waterside design options.
 
Land drainage
 
You should consider how any existing land drainage strategy will interact with the river works. For example, you might choose to discharge rainwater through ditches linking into the river – this helps create a variety of habitats. Bad drainage design can lead to many problems. For example, poorly designed outfalls can lead to local erosion damage, possibly increasing flood risk or damaging habitats.
 
Flood risk management
 
The features of the flood risk management system that need to be considered include (in some countries you may need to undertake a flood risk assessment as part of any works):
  • Land-based loadings (e.g., soil, water, buildings, vehicles, etc.).
  • Current flow, waves, boat and propeller wash, and risk of illegal mooring.
  • Anticipated future river uses.
  • Durations of all forces, especially peak forces.
  • Frequency and duration of inundation of the area of waterside under consideration .
  • Ground conditions and geology.
  •  Gradients of any maximum slopes necessary in the space available and stability of substrates at those gradients.
  •  The strength and durability of individual components and the elements included in the design.
  • Water chemistry and factors affecting growth of plants such as wetted area.
  • The overall desired lifespan of the design.
  • Monitoring and maintenance.
You need to set out your proposals clearly, both in terms of what you propose to construct and how.
 
Existing greenspace
You should always encourage and promote natural colonisation in the design as this will create locally appropriate communities. Wetlands are an important natural resource, storing and filter water, capturing carbon, providing food and fuel, and supporting a wealth of uniquely adapted wildlife. Working with natural processes will improve local conditions for valued flora and fauna.
 
However, planting may be needed when:
  • there appears to be limited scope for such natural colonisation, such as a lack of a seed bank that can reach the site naturally.
  • early vegetation establishment is required for slope stability (seek advice from a geomorphologist)
Timing of the planting and pre-establishment of species of the correct genetic strain is an important consideration (seek advice from an ecologist to ensure that plants are of appropriate species and, wherever possible, of local origin). Plants also need to be selected at the correct size, planted at the correct level, and in appropriate groupings to ensure maximum chance of establishment. Some invasive species that may be particularly problematic This risk needs to be assessed and if necessary protection measures put in place.
 
Archaeology and heritage
 
It is important to check whether you are likely to affect any features of archaeological or heritage importance. Wetlands can contain a unique record of our past through their well preserved organic archaeological remains.
 
Education, aesthetics and art
 
In any project you should take every opportunity to make design references to environmental issues and social history. Extending the landscape design from the water’s edge can produce striking landscapes. You should also consider seasonal changes in appearance. Last but not least all of these installations need to be explained to the observer, or they will be misunderstood and may even be criticised. Environmental signage should be eye-catching, artistic and robust.
 
Sustainability of materials
 
You should use recycled materials in designs wherever feasible, appropriate and functional. Pre planning ensure that faggotts or other natural material can be sourced when they are at their optimum state for instalation. Wherever possible, when choosing other construction materials, you should opt for those of the greatest surface roughness for claddings. This is to provide stable colonisation by surface-dwelling algae and plants.
 
Management and communication during the project
This is a crucial element to the success of all river restoration projects. It can manifest itself in many ways from stakeholders’ expectations, appropriate communication between project designer and contractor, early considerations of necessary consents, through to no/limited site attendance from the project designer. If not managed efficiently, such elements can result in project delays and the inability to secure funding.

 

Now go to Step IV – Sharing best practice

  • Stream and Watershed Restoration: A Guide to Restoring Riverine Processes and Habitats

This textbook covers both new and existing information following a stepwise approach on theory, planning, implementation, and evaluation methods for the restoration of stream habitats. It is illustrated with case studies from around the world (Purchase here).

  • River Restoration Centre (1999, 2002) Manual of River Restoration Techniques
The manual demonstrates the application of practical river restoration techniques in different river types. It includes specific detail about the design and implementation of each technique. View here
  • Estuary Edges
Developed by a team of engineers and ecologists, this guidance looks in detail at four key approaches to estuary bank design. View here