Density (people/km²)
< 100
100–500
500–2k
2k–5k
5k–10k
10k–20k
> 20k
Watercourses
river
tidal
canal
Flood zones
Zone 2 (1-in-1000)
Zone 3 (1-in-100)
Still water
inland (lake/reservoir)
tidal (sea/estuary)
Bathing waters 🏊 (current classification)
Excellent
Good
Sufficient
Poor
un-assessed
UWWTD-sensitive area extent
Source Protection Zones (groundwater)
SPZ Zone 1 (inner — 50-day)
SPZ Zone 2 (outer — 400-day)
SPZ Zone 3 (catchment)
SPZ Zone 4 (special interest)
Sites of Special Scientific Interest
SSSI (biodiversity)
Shellfish protected areas
WFD shellfish water
Storm overflows (2024 hours)
< 10 h
10–100 h
100–500 h
500–1500 h
> 1500 h
Nitrate Vulnerable Zones
NVZ (2021 designation)
Drinking-water source areas (surface)
DWPA SW (At Risk for sewage pressures)
DWPA SW (other)
Surface-water Safeguard Zones
SGZ SW (At Risk)
SGZ SW (other)
Groundwater Safeguard Zones
SGZ GW (additional protection)
Synthetic sewers (illustrative)
trunk (≥ 1000 PE inferred)
capillary
bridge (inferred — fills topographic gap)
Inferred from D8 topography · not a real sewer atlas
Synthetic WwTW catchments (illustrative)
Strain ratio = synthetic / UWWTR official p.e.
under-reaches (ratio < 0.3) — pipe data critical
moderate under (0.3 – 0.5)
topographic match (0.5 – 2.0)
moderate over (2.0 – 3.0)
over-reaches (ratio > 3.0) — model artefact
no UWWTR data (sub-2000 p.e. works)
🏭 WwTW location
Pumping stations ⚙
water-company sewer pumping station
Click → PCS-100 base sensitivity
WwTW points 🏭
sewage treatment works
Click → WCS-100 base sensitivity factsheet
Click trace
downstream impact path
upstream contributors
overland flow path