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Description:
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The main objective of this research is to devise a risk -based methodology for
developing emergency operation schedules (EOS ) . EOS are decision tools that provide
guidance to reservoir operators in charge of making real -time release decisions during
major flood events . A computer program named REOS was created to perform the
computations to develop risk -based EOS . The computational algorithm in REOS is
divided in three major components : (1 ) synthetic streamflow generation , (2 ) mass
balance computations , and (3 ) frequency analysis . The methodology computes the
required releases to limit storage to the capacity available based on the probabilistic
properties of future flows , conditional to current streamflow conditions . The final
product is a series of alternative risk -based EOS in which releases , specified as a
function of reservoir storage level , current and past inflows , and time of year , are
associated with a certain risk of failing to attain the emergency operations objectives .
The assumption is that once emergency operations are triggered by a flood event , the risk
associated with a particular EOS reflects the probability of exceeding a pre -established
critical storage level given that the same EOS is followed throughout the event . This
provides reservoir operators with a mechanism for evaluating the tradeoffs and potential
consequences of release decisions .
The methodology was applied and tested using the Addicks and Barker Reservoir
system in Houston , TX as a case study . Upstream flooding is also a major concern for
these reservoirs . Modifications to the current emergency policies that would allow
emergency releases based on the probability of upstream flooding are evaluated . Riskbased
EOS were tested through a series of flood control simulations . The simulations
were performed using the HEC -ResSim reservoir simulation model . Rainfall data
recorded from Tropical Storm Allison was transposed over the Addicks and Barker
watersheds to compute hypothetical hydrographs using HEC -HMS . Repeated runs of
the HEC -ResSim model were made using different flooding and residual storage
scenarios to compare regulation of the floods under alternative operating policies . An
alternative application of the risk -based EOS in which their associated risk was used to
help quantify the actual probability of upstream flooding in Addicks and Barker was also
presented . |