850 million cubic metres, downhill
Angat Downstream
A 2D hydraulic simulation of a breach at Angat Dam, Norzagaray, Bulacan — a 131 m rockfill embankment holding about 850 million cubic metres of water above one of the most densely settled floodplains in the Philippines. Five breach scenarios are routed over real 30 m terrain and reported for every barangay in the flood path: how deep the water gets, how soon it arrives, and how many people are in it.
Scenario
The scenarios side by side
Same terrain, same solver, same
exposure method — only the breach differs. Click a card to switch the whole dashboard to that scenario — the scorecards, map, hydrograph and tables all
follow. The one in use is outlined.
Every barangay in the flood path
| Barangay | Municipality / city | Population | Exposed | % area wet | Max depth | Avg. depth | Arrives | Peak speed |
|---|
Exposed population is the barangay's 2020 census count
multiplied by the fraction of its area under more than 0.3 m — people are
assumed evenly spread within a barangay, which is the honest limit of the
available data. "Arrives" is the 5th-percentile arrival time across the
barangay's flooded cells, i.e. when water first reaches it. "Peak speed" is
taken over flooded cells only, and is inflated inside the Angat gorge for
the same reason depths are there — on the floodplain it runs 2–9 m/s. In the
typhoon scenario a barangay marked pre was already under water from
the storm before the breach, so no dam-wave arrival time is meaningful for
it.
Breach outflow
Discharge through the breach, from the parametric breach
model routed against the reservoir's own stage–storage curve. The selected
scenario is drawn solid; the others stay for comparison.
Towns by population in the flood
Municipalities and cities ranked by exposed population for
the selected scenario. Bars are exposed population; the number after each is
the share of the municipality's land area under more than 0.3 m.