Flood hazard along Saudi wadis: height above the nearest channel, and three exposure zones covering 295,349 km2

The height of every cell above the nearest channel it drains to, at 90 m for the whole Kingdom, and three exposure zones: under 2 m, 2-5 m and 5-10 m above the channel.

The exposed area totals 295,349 km2 (15.35% of the country), of which 184,460 km2 is in the highest zone, with polygons of that zone and a per-governorate table.

Who it is for

Civil defence and emergency management, municipalities and planning offices, stormwater engineers, insurers and researchers.

Method: what we add to the raw data

• What gets flooded is governed not by absolute elevation but by height above the channel the land drains to: ground at a thousand metres may sit in a valley floor, and ground at a hundred metres on a high edge.
• For every cell the vertical height above the nearest channel along its own flow path was computed, not above the nearest channel in a straight line; this is the definition of this index in the hydrology literature.
• A channel here is one receiving 25 km2 or more, and zones are counted only beside such channels, since a ravine draining a few square kilometres poses no appreciable flood hazard.
• Three zones are set at two, five and ten metres above the channel, the lowest being the most exposed.
• The source is an open global elevation model at 15 m, prepared at 90 m, with depressions filled only partially to twenty metres to preserve genuine closed depressions.

Product details

Spatial layers

• governorates_flood — polygons, 121: Governorates with their exposed area
• very_high_zones — polygons, 18,156: Polygons of the highest zone

Raster files (GeoTIFF)

• D116_flood_zones_90m.tif — 27,211 × 20,409, 90 m: Exposure zones (three classes)
• D116_hand_90m.tif — 27,211 × 20,409, 90 m: Height above the nearest drainage channel

Tables

• D116_governorates_flood.csv — 121 rows: Exposure per governorate
• D116_very_high_zones.csv — 18,156 rows: Highest zone polygons table

Limitations

• This is a terrain-based exposure index, not a flood simulation: it excludes rainfall intensity, return period, runoff volume and hydraulic structures such as dams, culverts and drains, all of which change what actually floods.
• A zone does not mean the land will flood, only that it lies that far below the channel; actual flooding depends on a particular rainfall event.
• At 90 m cells, urban channels, culverts and retaining walls do not appear; this is a basin and master-plan scale product, not a parcel-scale one.
• Major cities have altered their drainage by earthworks and channels, which the elevation model does not know.
• The 25 km2 threshold is a methodological choice: lowering it widens the zones considerably in the highlands.
• The elevation model derives from imagery acquired up to 2024, so later earthworks are not represented.
• The area measured from the boundary used here is 1,925,091 km2, less than the commonly cited official figure of about 2,150,000 km2; the difference is between a declared figure and an area measured from a digital boundary.

FAQ

How long does delivery take?

Up to 6 hours after payment is confirmed.

How long does the download link last?

24 hours, and it is renewed free on request.

Can I get a refund?

Digital products are not refundable once downloaded — unless the file is defective or does not match the description, in which case it is replaced or fully refunded.

What does the licence allow?

Commercial use is allowed for you and the organisation you buy for; resale or redistribution is not.