5 things developers need to know about River Condition Assessments and BNG

Developers with projects that involve, abut, or are simply nearby waterways have extra work when it comes to biodiversity net gain (BNG) planning applications: River Condition Assessments.

The River Condition Assessment (RCA) differs from BNG condition assessments in that it takes a broad, holistic view of the stretch of river related to your site and considers:

• What things positively impact the river ecosystems that are created in that area?
• How will your development impact or encroach upon this stretch and downstream areas?

Defra’s Statutory Biodiversity Metric user guide provides direction regarding data collection and waterway classification, and the Statutory Biodiversity Metric tool has required fields for final calculations for a river’s condition, and encroachment values. However, developers will need to undertake an RCA to gather and evaluate data to determine the values to enter into the metric’s tool as part of their BNG application.

Below we’ll examine 5 things developers should keep in mind regarding River Condition Assessments and biodiversity net gain.

1. If water runs through — assessment is a must

BNG requires RCAs not just for rivers, but also for other watercourses, such as priority river habitats, canals, streams, and similar. These also include adjacent features like fishways, and disconnected ponds.

Exceptions include:

• Ditch — artificially created to convey water (more than 4 months per year), less than 5 metres wide; these have a simpler condition assessment provided in the statutory guidance.
• Culvert — artificial construction (covered channel or pipe) created to ensure drainage.
• Estuary — part of an intertidal zone; areas higher than the low tide mark will be separately assessed as an intertidal habitat, such as a mudflat.

2. River Condition Assessment requires a qualified assessor

Although you may have an ecologist lined up to assist with BNG application planning, separate credentials are required to provide both field-based and desk-based assessment of any watercourse on or near your property. Your ecologist may have these credentials, or you may need to enlist another individual who has successfully completed the Modular River Physical Survey (MoRPh) technique training to assess watercourse physical structure and habitats.

The MoRPh surveys assess the river’s banks, bank face, and riverbed in replicated surveys along at least 20% of the river’s sub-reach — a section of the river that makes for a more manageable size for surveying.

• The MoRPh approach includes a set of 5 surveys (a MoRP5 survey), which are taken in a row next to each other.
• The length of each survey is the same across the sub-reach and defined by the river’s typical width.
• Each set of 5 is repeated at least twice through the watercourse, as many times as necessary to cover 20% of the river’s sub-reach.
• A typical sub-reach may require between 2 and 5 sets of MoRPh surveys.

The idea is to get representative points. First, the assessor must walk the length of the project’s line with the river, and then choose points within it that are accessible and exemplify areas of the river that will be most and least impacted by your project. For example, if your project disturbs soil, you may need to assess the impact the activity could have downstream.

When the field work is complete, it’s time to combine the field surveys with a desk-based survey that classifies the characteristics of the river. The result indicates the river conditions. This is your benchmark from which you’ll need to consider your project impact and plan for 10% BNG.

3. It’s not just the river, but also the riparian edge

The MoRPh methodology is applied not just to consider river condition, but also the watercourse’s riparian edge — the area of land around the riverbanks that influences the quality of the river. Typically, the MoRPh survey involves 10 metres from the top of the riverbank.

It requires training to determine the exact start of the riverbank. Banks of steep valley rivers may reach a very different place from what you are expecting. Banks of shallow, meandering rivers may be somewhat easier to map out, but still need a credentialed evaluation. Keep in mind that rivers could require consideration even if they are more than 10 meters away from your project boundary.

Are you confident that the nearby watercourse’s bank is significantly more than 10 metres away? If not, take a precautionary approach and enlist a qualified RCA assessor to conduct the MoRPh survey to avoid a surprise late in the project.

4. Achieving 10% BNG is different for rivers — offsite elements must be considered

Assessments for BNG occur within site boundaries, but for RCAs, you may need to plan to look beyond your project site — upstream, downstream, and even across the river.

You may have used technology like satellites and AI to assess habitat, while an ecologist verifies your data and makes recommendations. Or your ecologist may complete the assessment in its entirety. Either way, these project area assessments for BNG planning are made within project site boundaries.

However, RCA surveys often require off-site assessments to determine where other conditions might affect the score of your river. The impact of your development might not happen to the section of the river where your project is located. It might occur downstream, and that might be something you need to mitigate.

So, it’s more of a connected system that you must consider. Every river has two banks, and you might be in control of only one. Your planning may necessitate that you work with the landowner of the other bank, on the other side of the river to achieve on-site BNG gains.

5. Encroachments are opportunities for BNG improvements

The MoRPh survey may reveal encroachments and negative impacts to river scoring. But here is where there is opportunity for your RCA assessor to recommend improvements for BNG. For example:

• If artificial materials reinforcing the bottom or sides of the river channel, such as bricks, concrete, or metal sheeting, the opportunity would be to replace these elements with a natural alternative.
• If agricultural or other runoff muddies the waters upstream from your project, the opportunity is to improve water quality — possibly introducing natural filtration, such as reed beds.
• If banks are artificial, the opportunity is to replace them with natural vegetation.
• If the riverbank or riparian zone is artificially encroached upon by structures, the opportunity is to relocate/remove structures to allow natural meandering of the river.

Separately to the RCA assessment the Statutory Biodiversity Metric tool requires calculating the degree of encroachment on the riverbank and the riverbed as a proportion of the total area.

If your assessor is completing an RCA for your site, make sure that they have also captured all the relevant detail for assessing encroachment for BNG.

A look to the future

The two major goals of River Condition Assessment — determining watercourse conditions and encroachments — in the future may be accelerated via satellite and AI solutions, like AiDash Biodiversity Net Gain Management System (BNGAI).

With satellite surveying and AI analysis, tech-collected data as well as desk-top surveys and field assessments could be computed and analyzed up front. This would free the qualified ecologist or RCA assessor to spend more time on evaluative conclusions and recommendations.

Click here for more information on AiDash BNGAI and its ability to include BNG benchmarking and planning as well as River Condition Assessments in BNG planning applications.

Justin Byrne, PhD MCIEEM 
AiDash Senior Ecologist – EMEA, R&D

Justin is an RCA trained ecologist, with particular expertise in BNG, remote sensing, and woodland ecology. Justin’s work and research has primarily focused on how we use modern technology to revolutionize how we do ecology; including the use of eDNA, satellites, and drones to study biodiversity and ecosystems in partnerships with The Woodland Trust, Forest Research, The Wildlife Conservation Society, Grown In Britain, and other organizations.