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Overview of Urban Drainage Flood Prediction Methods and Approaches J.Y. Chen 1 and B.J. Adams 2 1. Water Survey Division, Environment Canada 2. Department of Civil Engineering, University of Toronto 2008. 05. 06. Presentation Outline. Urban drainage modeling approaches

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Presentation Outline

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  1. Overview of Urban Drainage Flood Prediction Methods and ApproachesJ.Y. Chen1 and B.J. Adams21.Water Survey Division, Environment Canada2. Department of Civil Engineering, University of Toronto2008. 05. 06

  2. Presentation Outline • Urban drainage modeling approaches • Analytical model development • Model evaluation and comparison • Conclusions

  3. Methods for Urban Drainage Flood Prediction • Statistical/stochastic methods • Flood frequency analysis • Regional flood frequency analysis • Time series analysis • Deterministic methods • Conceptual models

  4. Deterministic Conceptual Modeling Methods Water budget Model inputs Model structure Runoff routing Model calibration Model verification Prediction

  5. Approaches Used for This Study • Design storm approach • Simulation approach • Continuous simulation • Event simulation • Derived probability distribution approach

  6. Analytical Model Development • Closed-form analytical models are developed with derived probability distribution theory • Probability distributions of runoff volumes and peak flow rates can be derived from probability distributions of rainfall characteristics

  7. Rainfall-Runoff Transformation • Runoff coefficient based • Extended form

  8. Rainfall-Runoff Transformation (Cont’d) • Infiltration based

  9. Analytical Model Statistic analysis of rainfall records Rainfall characteristics, e.g., rainfall event volume, duration & interevent time Overflow Storage facility Exceedance probability of a runoff spill volume Probability distributions of rainfall characteristics Rainfall-runoff transformation Average annual volume of spills Average annual number of spills PDF or CDF of runoff event volume Expected value of runoff event volume Average annual runoff volume Average annual runoff control efficiency

  10. Rational Method • Peak flow rate • Runoff volume • Storage Post-development peak Pre-development peak Tbase=2tc or 2.67tc

  11. Simulation Models • Event simulation models • OTTHYMO (Canada) • HEC-HMS (US) • SWMM (US) • Continuous simulation model • SWMM

  12. Case study:Don River Watershed

  13. Harding Park stormwater detention facility

  14. Model Calibration Rational method OTTHYMO

  15. Model Calibration (Cont’d) HEC-HMS SWMM

  16. Calibration of Analytical Models

  17. Model Verification

  18. Model Verification (Cont’d)

  19. Conclusions • Peak flow rates from event simulation models appear to be lower than the results from continuous simulation model • Event simulation models appear to be more conservative than continuous simulation model for runoff volume estimation

  20. Conclusions (Cont’d) • The closed-form analytical models developed with derived probability distribution theory, are capable of providing comparable results to continuous simulation results • Different models may vary not only in modeling approach, but also in the level of complexity, it can be challenging to select an appropriate model with a desired level of performance

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