Geophysical Cascade Lab RISK: CRITICAL DEBRIS WAVE

Himalayan Cascading Hazard Simulator: Landslide Dam & Outburst Flood Dynamics

Transboundary Corridor v2.4 (USACE/Froehlich Hybrid)

Transboundary Gorge Elevation & Cross-Section View

Dam Height: 68.4 m

Backwater Lake: 14.2 M m³

Breach Peak Q: 4,820 m³/s

Froude No. (Fr): 1.84 (Supercritical)

Time Elapsed: T + 00:14:20

Phase 3: Catastrophic Dam Overtopping & Breach

Stn 1: Upper Gorge (2.5 km) 12 min

4,620 m³/s

Depth: 18.4 m Vel: 9.8 m/s

Stn 2: Border Settlement (9.0 km) 38 min

3,240 m³/s

Depth: 11.2 m Vel: 7.1 m/s

Stn 3: Lowland Fan Bridge (24 km) 94 min

1,890 m³/s

Depth: 6.5 m Vel: 4.2 m/s

Downstream Hydrograph & Sediment Volume Fraction (%) Blue = Water (m³/s) | Orange = Sediment Solid Load (%)

Corridor Scenario Preset High Himalaya Analogs

Slope Incline Angle (θ) 48°

Detachment Volume (M m³) 4.2 M m³

Monsoonal Pore Pressure (Ru / Sat %) 82%

Valley Floor Choke Width 45 m

Trigger Mechanism

Cloudburst

Seismic 6.8

Ice-Rock Fall

Breach Initiation Mode

Overtopping

Internal Piping

Shear Burst

Transboundary Settlement Impact & Evacuation Windows

Cascading landslide dam outburst floods (LDOFs) exhibit hyper-concentrated solid loads (>35% volumetric sediment), resulting in hydrodynamic forces exceeding conventional clear-water flooding by a factor of 4.2×.

Zone / Asset	Arrival	Peak Q	Boulder Kinetic Energy	Status
Stn 1: Upper Gorge Intake	+12 min	4,620 m³/s	42.5 MJ	Total Inundation
Stn 2: Border Village & Bridge	+38 min	3,240 m³/s	18.1 MJ	Severe Shear Failure
Stn 3: Downstream Market Fan	+94 min	1,890 m³/s	4.8 MJ	Evacuate Banks

Physical Mechanics & Modeling Equations

This computational platform calculates peak breach discharge (Q_p) and hydrograph wave propagation using validated geomorphic relationships:

Costa (1985) & Froehlich (2016) Outburst Formulation:
Q_p = 0.607 × (V_w)^0.295 × (h_d)^1.24 where V_w is backwater volume (m³) and h_d is effective landslide dam height (m).
Coulomb Failure Criterion & Saturated Pore Pressure:
τ = c' + (σ_n - u) tan(φ'). Elevated monsoonal pore pressure u reduces effective normal stress, initiating sudden mass detachment.
Debris Slurry Viscosity: Takahashi non-Newtonian flow model approximating grain collisional shear and bed entrainment.