Dynamic rule curves for flood control of a multipurpose dam

• We propose dynamic rule curves for flood control (DFCRCs) of a multipurpose dam.
• We develop an approach for computing the DFCRCs adapted to a predicted flood.
• The DFCRCs are superior to existing ones for the reservoir whose size is limited.

The balance of using the normal retention capacity of a multipurpose dam between flood control and conservative objectives is usually necessary for operating its reservoir. This paper proposes dynamic flood control rule curves (DFCRCs) for the dam whose reservoir size is too limited to manage the uncertainty in design flood occurrence by current practice (i.e., flood control rule curves, FCRCs). The DFCRCs effectively adjust the allocated spaces of the limited reservoir to satisfy both referred purposes for each predicted flood. Hence, an approach for computing the DFCRCs is composed of a combination of a flood prediction model and a storage routing method. The prediction model estimates the volume and peak properties of an arriving flood, and takes a design flood with its characteristics being equal to the estimates as the expected one. The DFCRCs of the predicted flood are calculated using the storage routing method. The computational approach for the DFCRCs of a small multipurpose reservoir against a wide range of floods has been developed to assess their operational performances by comparing with those of the existing FCRCs. Results have indicated that the operational performances of the DFCRCs and the FCRCs are equally acceptable for an extremely large flood of return period >10,000 yrs. However, when dealing with the flood of recurrence interval ranging from 200 yrs to 3 yrs, the DFCRCs are better because they successfully secure the dam, protect the areas downstream from being inundated, and meet the water demands during consecutive dry season.