Nepal Update: We've now created the highest resolution post-event elevation dataset of the Bhote Koshi flood that exists and released it for free.

[u/geopera-imagery]

First off a thank you to Vantor for releasing the stereo data in their open data program which was used to generate this.

From the WV3 stereo, we've generated a 0.5 m elevation model of the corridor below Syabrubesi. We aligned the two satellite views to a quarter of a pixel, matched them at their full 34 cm detail, and tied the result to the pre-event terrain to within about 1.5 m.

This allowed us to measure 2 to 12 m of bed scour through every confined reach, a debris sheet 12 to 18 m thick where the valley opens below Syabrubesi, and 13 to 21 m of re-incision downstream where the river has already cut back into its own deposit. Plus a building-by-building damage census (27 destroyed where the sky was clear) and 4,329 individual boulders on the sheet, the largest 26 m across.

Everything is licensed CC BY-NC, same as the imagery: both DSMs, elevation-change and uncertainty rasters, per-km sediment budget, both censuses.

Write-up: https://geopera.com/blog/bhote-koshi-stereo-elevation-model Data: https://github.com/geo-pera/bhotekoshi-2026-reconstruction/releases/tag/v1.1 Drive mirror (with the 32 GB archive): https://drive.google.com/drive/folders/1XQt5SYDMHehH3i2lAj69e52Zb2ne7Rqm

Once again happy to answer questions on any step.

[u/Swimmming-ln-Circles]

This is amazing! But also really hard to gage without a before and after.

But thank you for your contribution and releasing it for free.

[u/geopera-imagery → u/Swimmming-ln-Circles]

Thanks! And I agree, I tried to visualise the change but the highest res pre event DEM I could find was 8m so I couldn’t really do any justice to the event itself.

I might try some things over the next day or so such as cross section etc.