PZGL Studios · Ngong Municipality · Interactive Screening Tool

Ngong Drainage Explorer

Filter, map, and inspect all 1,402 locations where Ngong's terrain-derived natural drainage overlaps mapped buildings and roads. This is a live companion to the board screening deck. Generated 23 August 2026 from Copernicus GLO-30 terrain and current OpenStreetMap data.

Ward
Priority
Asset

Where the filtered set breaks down

Click any bar to toggle that filter

By ward

By priority

By asset type

Map

Drag to pan, scroll to zoom, click a point or ward for detail
The 20 m contours and terrain-predicted flow paths come from Copernicus GLO-30. The surface water network shows locally mapped rivers and streams from OpenStreetMap, together with water bodies from JRC Global Surface Water. Regional RiverATLAS centrelines are excluded at every zoom level. The municipal boundary remains provisional; see the funding ask below.

All flagged locations

Flow-path distance is the shortest modelled separation between the asset geometry and the nearest terrain-predicted flow path. It does not refer to a mapped river, stream, or water body.

Screening strengths and limitations

Accurately:

  • Shows mapped buildings and roads that intersect or sit close to terrain-derived flow paths
  • Compares wards, priorities, and asset types before field checks are planned
  • Supports selection of a bounded set of locations for municipal and community verification
  • Identifies where confirmed boundary, drainage, incident, and survey data are still needed

Inaccuracies:

  • Flood causes and flood history at a specific location are not confirmed
  • Missing OpenStreetMap drainage features do not prove that no drain exists
  • Drainage design, size, condition, and capacity are not assessed
  • Capital works cannot be approved without field verification, survey, and engineering review

Funding ask: strengthening the evidence base

El Niño seasons can bring periods of unusually heavy rainfall that expose drainage weaknesses and disrupt roads, homes, and public services. Funding the evidence gaps below would help Ngong prepare before high-risk rains by confirming where water moves, what drainage exists, and which flagged locations require field action. This screening does not predict a specific El Niño event or confirm flooding at any location.