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The NWS S i mp lified D am B rea k Model SMPDBK Model

The NWS S i mp lified D am B rea k Model SMPDBK Model. 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 Manning’s equation.

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The NWS S i mp lified D am B rea k Model SMPDBK Model

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  1. The NWS Simplified Dam Break ModelSMPDBK Model

  2. 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 Manning’s equation.

  3. 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

  4. 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

  5. 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;

  6. 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.

  7. SMPDBK Model

  8. SMPDBK Model Time to Peak (Tp): Manning Equation:

  9. SMPDBK Model Time to Flooding and Deflooding of Elevation hf:

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