2D Simulator

Slide impact, wave propagation and run-up on the real fjord

A rock mass slides off the north wall beside the 2025 South Sawyer Glacier terminus and displaces the fjord. The non-linear shallow water equations carry the wave down Tracy Arm, through Sawyer Island and the bends, towards Holkham Bay. Everything runs in your browser; the 120 m grid takes about 10 s.

Scenario
Landslide
Volume64 M m³
2.0 M m³120 M m³
Impact velocity78 m/s
20 m/s110 m/s
Thickness100 m
20 m160 m
Geometry
Slide width900 m
200 m1400 m
Travel azimuth190°
170°SW = across fjord260°
Underwater runout (assumed)600 m
200 mcontrols toe run-up1600 m
Manning n (bed friction)0.030
0.0150.060
Solver
Grid resolution
Simulated time
Ready

Tracy Arm, UTM 8N

Loading the fjord terrain…
t = —
Free-surface elevation η (m)
−60−150+15+60

Terrain: USGS 3DEP 1/3″ DEM, hillshaded. Water depths: NOAA multibeam surveys (2005–2018); the fjord head uncovered after 2018 is trough-filled (Survey layer). The slide scar, 2025 terminus and 481 m trimline positions are approximate.

Modelled vs observed

Wave run-up (≥ 300 m from slide)

—m

Observed 481 m trimline

Max wave at Sawyer Island

—m

Observed ≥ 30 m (kayaker photos)

Wave energy (peak)

—TJ

Arrival, mid-arm vessel route

—

Water hit by ≥ 2 m waves

—km²

Small-craft hazard footprint (Hazard layer)

Virtual tide gauges

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Modelled free-surface elevation η(t) at fixed points down the fjord. The 2025 Juneau tide gauge, far outside this domain, recorded 0.36 m.

Energy budget

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Potential (½ρgη²) and kinetic (½ρh|u|²) wave energy. Friction, numerical dissipation and wave breaking (absorbed by the shock-capturing scheme) drain it as the wave runs out.

Wave decay along the fjord: 2D solver vs Heller–Hager

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Points: largest modelled η in each 500 m band of water-path distance from the impact. Lines: Heller & Hager (2010) 2D decay laws for the same slide in 200 m of water. Wave-channel laws cannot spread energy sideways or reflect it off bends, so the 2D curve falls below them away from the source.