Integration of Probabilistic and Physically-Based Modelling with Optimization Methods for Stormwater Infrastructure Rehabilitation.

Abstract
Probabilistic stormwater flows are determined using kinematic wave routing methods and long-term historical rainfall. A multiobjective chance constrained optimization model, subject to constraints based upon physical modelling and historical rainfall data, is applied to a stormwater drainage network in Atlanta, Georgia. The optimization model objectives include minimization of total rehabilitation costs and maximization of stormwater system reliability. Rehabilitation alternatives include replacement, upgrading and varying the design capacity of the drainage system. This modelling approach can be used to develop trade-off relationships between the minimum rehabilitation cost and the probability of failure of the drainage system due to stormwater events. Results of optimization with a simplified runoff model (the rational formula with intensity-frequency-duration curves derived from Gumbel statistical methods) are compared to the results obtained by kinematic routing of stormwater through the channels and pipes of the network, using long-term historical rainfall as input.
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