OpenWater

README excerpt

# climate-simulator

An interactive 3D simulator for extreme rainfall over real urban terrain. You load a city, choose a
storm, and watch where water goes — with tunable rainfall return period, ground absorption, and
drainage capacity.

First city: São Paulo. Goal: any region on Earth.

> **This is not for navigation, regulatory, permitting, or other legal purposes.**
> It is an exploratory and educational tool for understanding *relative* flood sensitivity — how the
> pattern of flooding responds to storm intensity, infiltration, and drainage. It is not a hazard map,
> it will never answer "will my house flood", and it does not model sewer network hydraulics,
> culverts, blocked inlets, reservoir operation, groundwater, or backwater from the Tietê.
> See [docs/NOT-MODELLED.md](docs/NOT-MODELLED.md) and the
> [validation report](docs/validation/index.html).

## What it actually is

A **2D shallow-water solver** — the Bates/Horritt/Fewtrell (2010) local-inertial scheme with the
de Almeida (2012) θ-stencil — running in **WebGPU compute shaders**, over a **bare-earth digital
terrain model** on a metric grid. Same governing equations as LISFLOOD-FP, SFINCS and Wflow.jl.
The simulation state never leaves the GPU, so rendering is free.

The physics is verified against analytic solutions (SWASHES) and the UK Environment Agency 2D
benchmark suite, and cross-checked against the City of São Paulo's own FCTH flood models. Every
result carries its full parameter set and its provenance.