NEPAL FLOOD MONITOR — Betrawati & Gerkhu Before/After

BEFORE12 Aug 2026

AFTER27 Aug 2026

⇆

Newly sediment-covered land (visual estimate, partial)

Flood deposits ≤120 m 120–300 m from deposits

A–D: visible built-up clusters in the hazard zone (people may be exposed or cut off — unconfirmed)

Before: mapped buildings | After: on deposit ≤120 m ≤300 m outside zones

Inferred flood flow direction (downstream)

Location & evidence

Event	Nepal flash flood — aftermath imagery
Area	Betrawati & Gerkhu, Nepal
Coordinates	27°58′10″N, 85°10′47″E (27.9694°N, 85.1797°E)
Before	12 August 2026
After	27 August 2026
Sensor	Copernicus Sentinel-2 (optical, 10 m native)
Type	Observed imagery (not simulated)
Credit	European Union, Copernicus Sentinel-2 imagery

What changed (visual reading)

The river channel is much wider; a pale grey-brown deposit band replaces green banks.
Deposits run the full length of the frame, past Gerkhu and Betrawati.
A side channel at Betrawati is also filled with deposits.
Clouds and shadows (lower right, after image) hide some ground.

Single buildings cannot be judged as damaged or intact at this resolution.

Flood direction (sourced)

Copernicus/EU Space reports that the 26 Aug 2026 flash flood entered Rasuwa District from the Tibet side and travelled downstream through the Bhote Koshi–Trishuli river system. In this north-up image that means from the top toward the bottom-left. The AFTER (27 Aug) image shows direction best, because the deposit trail marks the flood path; the BEFORE image only shows the old narrow channel. Arrows are traced by us from the deposit.

Houses & colonies (OpenStreetMap)

Press “Houses & colonies” to load mapped buildings and named places from OpenStreetMap (needs internet).

Nudge overlay ~20 m:

Before = mapped buildings (OSM is the current database, not the image date). After = same buildings coloured by distance from the flood deposit we mapped. OSM coverage is incomplete, alignment is approximate, and a building near the deposit is not confirmed damaged.

About this event (sources)

Flood on 26 Aug 2026; trigger still under study (ice–rock avalanche / glacier collapse; lake outburst also discussed).
Betrawati–Rasuwagadhi road (42 km) reported damaged.
Copernicus EMS activated EMSR927 (flood extent + damage grading). In the Syapru Besi area it found >240 buildings destroyed, 32 damaged (not this image area).
An IKCEST/China DRS4BR analysis traced an ~80.6 km corridor from Gyirong to Phirkep–Devighat (preliminary).
Casualty numbers keep changing: use official NDRRMA reports.

EU Space: this image pair
ESA: Nepal flash flood imaged by satellites
ESA: wider view of the whole flood path
Copernicus EMS EMSR927
IKCEST roads-bridges-buildings report
NSET situation report #04 (29 Aug)
HOT/HDX buildings & roads (OSM)

Possible exposure points

We cannot know where people actually are. A–D mark clusters of buildings visible in the before image that lie inside the orange/yellow hazard zones around the deposits. People there may have been exposed, evacuated or cut off from roads — unconfirmed. Real rescue information comes only from official sources (NDRRMA, Nepal Police, Nepal Army, local authorities).

A Betrawati, junction side
B Betrawati, riverside houses
C Gerkhu, north-bank cluster
D Gerkhu, south-west cluster

Terrain metrics

Newly covered area	≈ 0.8 km² visual estimate, partial lower bound. Method: colour thresholds on both images (new grey-brown sediment outside the old channel, clouds excluded); scale from the 250 m scale bar (≈1.4 m/pixel). Misses some areas.
Channel width	Data unavailable (not measured)
Elevation change	Data unavailable (no matching DEMs)
Damaged buildings	Data unavailable

Locator map: world → village

Base maps: OpenStreetMap, Sentinel-2 cloudless 2023 (EOX). Not the flood-date imagery. The red box (after “Houses & colonies” loads) is the approximate area of our satellite image.
Open in OpenStreetMap · Google Maps · Copernicus Browser

Sources

Copernicus Browser
Copernicus Emergency Management Service
NASA Worldview
OpenStreetMap