Natural Flood Management in Gwynedd: Screening with NatureInsight, shaping with local knowledge

Elen Mai Williamson and Cari Wyn, Assistant Engineers at Ymgynghoriaeth Gwynedd Consultancy (YGC), developed the funding application for the two sites using NatureInsight in Scalgo Live.

"We used NatureInsight to identify and prioritise potential NFM sites as part of the grant application".

Elen Mai Williamson

Criccieth was chosen with recent flooding still fresh in memory. In 2022, the town experienced an intense cloudburst, close to a hundred millimetres in about five hours, sending surface water through streets and into properties. Beyond that event, Criccieth has a longer record of flood incidents. The surrounding landscape is largely improved grassland, stitched with fields and punctuated by pockets of ancient woodland. In short, it’s a catchment with both space for NFM and ecological opportunity.

Waunfawr has a steeper topography and is more channelised by roads and culverts with limited capacity. Several properties have been affected across seven events in the past twenty years. The land cover is a patchwork, but the feature that draws the eye is the peatland higher up in the catchment. For the YGC team, that hadn’t previously worked a peat catchment, this introduced a fresh NFM avenue.

NatureInsight entered the picture early.

"We used NatureInsight to identify and prioritise potential NFM sites as part of the grant application," Elen explains. "We mainly filtered the analysis by looking at NFM measures that create the most storage volumes, as our main priority in these catchments is to reduce flood risk."

"It gave us a quick way to identify and visualise NFM opportunities and was a useful starting point for landowner discussions".

Elen Mai Williamson

The cost-benefit tool was also helpful in assessing feasibility, giving realistic cost estimates.

"The cost estimates in NatureInsight appeared very reasonable based on past examples," Elen continues.

The early screening didn’t just quantify flood storage. With NatureInsight’s co-benefit outputs, the team could show habitat uplift and carbon effects alongside flood mitigation.

In Criccieth, NatureInsight helped identify buffer strips, large woody debris, and runoff attenuation as the main NFM opportunities. In Waunfawr, lower-lying fields suited tree planting. Higher up in the peatland, grip blocking was considered the main intervention.

With funding confirmed, the team carried out site visits to ground-truth the potential NFM opportunities highlighted in the desktop analyses. These visits helped refine which land parcels would be most suitable for interventions, taking into account factors not visible in mapping alone.

Cari describes the continued process: "We also invited landowners for a drop-in session to talk about the plan and to explore collaboration. For example, in Waunfawr, landowners showed a lot of enthusiasm for the plans. Local knowledge is very useful and helps us shape the plans further."

At the same time, not all landowners’ plans aligned with the identified NFM opportunities. In Criccieth, one major landowner was already making changes to land use, leaving limited scope for NFM measures. In these cases, NatureInsight was helpful as it allowed the team to remove parcels or fix specific interventions and then recalculate the overall summary.

"We mainly filtered the analysis by looking at NFM measures that create the most storage volumes, as our main priority in these catchments is to reduce flood risk."

Elen Mai Williamson

All in all, Elen and Cari agree that the use of NatureInsight was very beneficial for the grant application.

"It gave us a quick way to identify and visualise NFM opportunities and was a useful starting point for landowner discussions," Elen concludes.

See the full webinar

For more inspiration on how to use Scalgo Live and NatureInsight, check the recent webinar “Insight to action: Local flood planning with NatureInsight”.