Linear Water Stream

Source: SRCE — Trame verte et bleue (France) Year: 2013-2015 Category: Transition risks · Sensitive areas · Critical areas · SRCE (France) Coverage: Country (France) Format: Boundary polygons Used in risk analysis: No (contextual layer; not used in materiality scoring)

What it shows

This layer maps the linear watercourse continuities of France's Green and Blue Network (Trame Verte et Bleue) — the "blue" element, formed by rivers and streams that connect aquatic and riparian habitats. It matters because activity along these watercourses can disrupt freshwater ecological continuity and the movement of species through the river network.

How it is built

France's Green and Blue Network is a biodiversity-preservation tool that integrates the maintenance and strengthening of natural-environment functionality into planning and development. It is defined at the regional level through the Regional Schemes of Ecological Coherence (SRCE). The ecological continuities it identifies include biodiversity reservoirs and ecological corridors; this layer captures the linear watercourse element of those continuities. It is delivered as mapped polygons.

How to read it

This is a boundary layer. A site that intersects, or lies close to, a mapped watercourse continuity should be flagged, since these streams are part of the connective freshwater network and any disruption can reduce ecological continuity.

Class thresholds

This is a categorical / presence (boundary) layer, not a model of a continuous physical quantity. The dataset is a set of 287,609 linear watercourse polylines from France's Regional Schemes of Ecological Coherence (SRCE). The symbolised field (SRCE Water Stream — Class 1 category, CLASSE1) is a qualitative continuity class — Fonctional (F), Natural (N) and Trame (T) — not a value binned into risk classes. There is therefore no measured flux and no numeric class breaks; the colours distinguish watercourse continuity type, not severity.

The "classes" are simply presence versus proximity: a site either overlaps (or lies near) a mapped watercourse continuity, or it does not. This layer is not used in materiality scoring (it is contextual), and the TOML defines no proximity trigger and no buffer distance, so there is no risk-flag threshold; the relevant consideration is overlap with, or closeness to, a mapped stream.

How these thresholds were set. Not applicable — there is no quantitative classification. The watercourse boundaries and their continuity categories are defined by the Regional Schemes of Ecological Coherence (SRCE), France (methodology after Allag-Dhuisme et al., 2010); Darwin uses those boundaries directly without any numeric classification.

Reference: SRCE — Trame Verte et Bleue, France (trameverteetbleue.fr).

Source

Regional Schemes of Ecological Coherence (SRCE), France — methodology after Allag-Dhuisme et al. (2010), via trameverteetbleue.fr.

Comparison with the WWF Risk Filter Suite

There is no global equivalent in the WWF Risk Filter Suite. As a French regional freshwater-connectivity dataset, it loosely supports WWF's ecosystem-condition / connectivity theme (S14_5), but WWF's connectivity input is the global functional-connectivity surface (Brennan, 2022), which Darwin does not yet hold globally. This layer is therefore a national extension rather than a WWF indicator.

Legend

Symbolised field: SRCE Water Stream - Class 1 category

Generated from darwin/layers/layer-linear-water-stream.toml and risk_indicator_pairs.toml (develop).