The NWS Simplified Dam Break Model SMPDBK Model

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The NWS Simplified Dam Break ModelSMPDBK Model
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SMPDBK Model Description
The NWS SMPDBK model computes the dam break
outflow from a simplified equation and routes the
outflow base on curves generated with the NWS
DAMBRK model. Flow depths are computed based on
Mannings equation.
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SMPDBK Limitations

• Backwater effects ignored
• No special effects included
• (e.g. bridges, dams, constrictions, etc.)
• Error range 0 - 10 Relative to NWS DAMBRK
• (when used within its limitations)
• Rapid, easy, low cost, emergency situations

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SMPDBK Model
PEAK OUTFLOW
Qo Spillway Flow Br Breach Width (avg.) tf
Time of Failure (hour) hd Height of Dam As
Avg. Surface Area of Reservoir in Top Portion
of Reservoir
Qbmax corrected for tailwater submergence and
dynamic effects
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SMPDBK Model
FLOW DEPTH
Depths computed from Manning Eq. for a known
discharge
The slope (S) is dependent on the upstream and
downstream reach If both subcritical, use
average slope If both supercritical, use
upstream slope If upstream slope is
supercritical downstream slope is subcritical,
hydraulic jump present compute two depths
If upstream slope is subcritical downstream
slope is supercritical, use critical slope (Sc
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SMPDBK Model
ROUTED FLOW
Routing of peak discharge via empirically derived
relationships (using DAMBRK model) as represented
via dimensionless parameters Qp/Qbmax, X/Xc, V,
and Fr.
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SMPDBK Model
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SMPDBK Model
Time to Peak (Tp)
Manning Equation
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SMPDBK Model
Time to Flooding and Deflooding of Elevation hf