Optimize Detention Pond Capacity

The purpose of this model is to use a simple detention pond model to optimize the pond height in combination with the orifice size in order to reduce peak discharge from the pond while spending as little as possible on constructing higher banks around the pond. There is a unit cost associated with increasing the banks of the pond, so the larger the pond, the more it will cost to increase it. Conversely, the greater the peak flow discharged from the pond, the higher risk to downstream properties, so it is advantageous to reduce the discharge as much as possible while still not increasing construction costs too much. This balancing act between orifice size and detention pond size is a good application to use GoldSim's optimization feature.

The model is built using a Pool element that represents the pool of water in the reservoir. The outflow from the pool is controlled by the size of the orifice and the height of water above the orifice, which is a function of the volume of water in the reservoir. This feedback between the volume and the discharge creates a balancing feedback loop. The optimization variable is defined using a Data element "Outlet_Area". The objective function is based on the construction cost of the dam versus how much the peak discharge can be reduced. Eventually, the cost of the dam overcomes the benefit of storing more flood water behind the dam. This model aims to help find the optimal balance between cost and benefit.

The optimization manager in GoldSim is used to run optimization trials. A screen capture shows how the objective function improves as more optimization trials are executed. 

Additionally, the objective function can be plotted against the optimization variable using GoldSim's built-in sensitivity analysis tool using an X-Y function plot.

Download the Model File: