The Impermeability KPI measures the percentage of land area covered by artificial impervious surfaces — buildings, roads, car parks, industrial pavements, and other sealed materials that prevent water infiltration. It is a direct indicator of soil sealing, one of the most irreversible forms of land consumption and a primary driver of urban ecological degradation.
This KPI is inverted: a lower impermeability percentage is ecologically better, because permeable soils support groundwater recharge, reduce surface runoff and flood risk, sustain plant growth, and maintain soil biodiversity. The indicator aligns with ESRS E4 (biodiversity) and E4-5 / AR 34b disclosures.
The impermeability value is computed by classifying each land cover pixel into one of three drainage categories — Impermeable, Semi-impermeable, and Draining — and then measuring the fraction of impermeable pixels within the site boundary.
where ROI = Region of Interest (site boundary), and water pixels are excluded from the denominator
Data are sourced from a multi-source land cover fusion layer combining ESA WorldCover, Impact Observatory LULC, Sentinel-2 composites, Google Dynamic World, and regional datasets, at 10 m spatial resolution.
Progress Bar. A horizontal linear scale comparing the impermeability percentage of the site against the control area, accompanied by a grade badge and a signed delta value.
Purpose: What share of the site's land surface is covered by impervious materials, and how does this compare to the surrounding control area?
Description: A horizontal scale from 0% to 100% shows the site score and the control area value as markers. A grade badge (A–E) appears alongside the site score. The delta value (Site − Control) is shown as a signed number (e.g., +20.07). Below the gauge, a short description reads: "Soil waterproofing comparison site-control." An ESRS tag E4 / E4-5, AR 34b is displayed.
Impermeable Land Share100%
How it's calculated: The site's impermeability percentage is derived from the dedicated impermeability classification layer. The grade uses inverted thresholds: A ≤ 20%, B ≤ 40%, C ≤ 60%, D ≤ 80%, E > 80%. The delta is Site value minus Control value.
Note: This indicator is inverted — lower values indicate better conditions.
Legend:
| Grade | Range (%) | Color | Meaning |
|---|---|---|---|
| A | 0–20 | ■ #00A67A | Predominantly permeable, natural soil |
| B | 20–40 | ■ #00DF80 | Low sealing, good water infiltration |
| C | 40–60 | ■ #FFD21E | Moderate urbanisation, growing risk |
| D | 60–80 | ■ #FF8B16 | High sealing, impaired ecosystem function |
| E | 80–100 | ■ #FF367F | Critical — nearly fully impervious |
Interpretation example:
If this bar shows 100% for the Site and 79.9% for the Control, it means the site is fully sealed — no permeable surface remains — while the surrounding area retains some soil infiltration capacity. This is the most critical ecological condition for soil health.
Assessment Sidebar Row. A row in the collapsible E4 Biodiversity grade panel on the left-hand assessment sidebar, displaying site and control values for soil permeability.
Purpose: How does the site's soil permeability (the inverse of impermeability) compare to the control area, at a glance?
Description: The sidebar row shows the label "Permeability" with two sub-values side by side: "Site" and "Control". The values are presented as a complement to impermeability (i.e., permeability = 100 − impermeability). The row appears under the collapsible E4 Biodiversity section of the assessment sidebar.
How it's calculated: The displayed permeability value is the complement of the impermeability percentage:
The grade reflects the same inverted scale as the main progress bar.
Note: This indicator is inverted — lower impermeability (higher permeability) indicates better conditions.
Interpretation example:
If the sidebar shows "Permeability — Site: 0% / Control: 20.1%", it means the site has zero permeable surface while its control area retains about 20% permeable land — confirming maximum soil sealing at the site.
Map Layer. An interactive map overlay showing the spatial distribution of impervious surfaces across the site and its surroundings, derived from the impermeability classification.
Purpose: Where are impervious surfaces located within and around the site boundary?
Description: The map displays a raster overlay in which each pixel is colored according to its classified drainage category. The layer is selectable from the "Select layer" dropdown panel in the map toolbar, which also shows an abbreviated button label "Impermeab." A tooltip panel displays: "The selected layer indicates the percentage of impermeable surface in the analyzed area. This value measures the degree of land cover with artificial materials." The layer is part of the Land Cover layer group alongside "High Detail" and "Naturality."
How it's calculated: The impermeability raster is generated by classifying each land cover pixel into three categories (Impermeable, Semi-impermeable, Draining). The layer is regenerated when the site's land cover task runs.
Note: This indicator is inverted — areas with higher impermeable coverage have worse ecological conditions.
Interpretation example:
If the map shows a dense red/high-impermeability overlay covering the entire site polygon while the surrounding control area shows grey/green (permeable surfaces), it confirms the site is a highly sealed urban environment with minimal soil infiltration potential.
Highlights Card. A compact KPI card in the Environmental KPIs sidebar panel on the Maps page, showing the control area impermeability value and grade for quick comparison.
Purpose: What is the impermeability level of the control area, for comparison with the current site?
Description: The card shows the label "Impermeability" with a downward arrow (↓) indicating an inverted indicator, followed by the grade letter (e.g., D) and the control area value (e.g., CA 79.9%). The arrow icon is the platform's standard signal for inverted KPIs.
How it's calculated: The control area (CA) value is the impermeability percentage of the surrounding control polygon, computed with the same formula applied to the ROI.
Note: This indicator is inverted — lower values indicate better conditions. The ↓ arrow on the card confirms the inverted nature.
Interpretation example:
If the card shows "Impermeability ↓ D — CA 79.9%", it means the control area has 79.9% impervious surface — already in poor condition (grade D), confirming the site sits in a heavily urbanised landscape.
| Source | Provider | Coverage | Resolution | Period |
|---|---|---|---|---|
| ESA WorldCover | ESA | Global | 10 m | 2020–2021 |
| Impact Observatory Annual LULC | Impact Observatory | Global | 10 m | 2017–2023 |
| Sentinel-2 SCL Annual Composite | ESA / Copernicus | Global | 10 m | 2017–present |
| Google Dynamic World Annual Composite | Global | 10 m | 2017–present | |
| OpenStreetMap Roads | OpenStreetMap | Global | Vector | Continuous |
| CLC+ Backbone | Copernicus | Europe | 10 m | 2018 / 2021 |
| CORINE Land Cover 2018 | Copernicus | Europe | Vector | 2018 |
| European Dominant Leaf Type | Copernicus | Europe | 10 m | 2018 |
| European Crop Map | JRC | Europe | 10 m | 2022 |
| Lombardy Forest Type | Regione Lombardia | Lombardy | Vector | 2023 |
The impermeability value is computed in two steps. First, a multi-source land cover fusion layer (CLC map) is generated by combining multiple satellite products and regional datasets. Second, a dedicated classification step reclassifies each pixel into one of three drainage categories: Impermeable (sealed artificial surfaces), Semi-impermeable (partially sealed or compacted surfaces), and Draining (natural permeable surfaces).
The classification uses the CLC pixel values to determine drainage category. The final KPI value is the fraction of impermeable pixels within the site boundary, multiplied by 100 to produce a percentage. Water bodies are excluded from the denominator — only land pixels are counted.
The same process is applied to the control area polygon for comparison. The delta value (Site − Control) indicates whether the site is more or less sealed than its surroundings.