Introduction
Ultimate Flood Consulting was contracted by The Centennial Park Trust in late July to analyse the current effectiveness of the park’s ponds, which have been engineered to act as a flood retention system. The project comprises of two components each focusing on an element crucial to the operation of the system namely an analysis focusing on flood management design and an analysis on water quality control.
Before development of the model, several assumptions had to be made for the project to continue. These assumptions were:
- Shape of all ponds was assumed to be conical.
- Evaporation, Rainfall, pipe and friction losses were negligible
- Flow was isolated to between ponds; i.e. outflow at one pond = inflow at connecting pond. Hence, flows due to alien sources were neglected.
Ultimate Flood Consulting has so far been able to develop a flood model that is capable of simulating the effectiveness of the Centennial Park flood retention system when subjected to heavy flows due to a major storm event. Through simulation results, Ultimate Flood Consulting was able to analyse the effects of a major flood event in a quantitative and qualitative manner.
Currently, Ultimate Flood Consulting is in the process of developing a model for an analysis on water quality control. Although the analysis is only at a partially complete stage, we are positive that this model will be complete before the deadline. A short description can be found below with further refinement of the model and results due in the near future.
Flood Modelling
Ultimate Flood Consulting utilised the simplicity and versatility of Microsoft Excel to develop our Flood Model Simulator. The model comprised of separate spreadsheets for each pond which were linked together to reconstruct the existing pond system in Centennial Park.
In order to assess the reliability and effectiveness of flood management in the pond systems, Ultimate Flood Consulting has produced a flood model that simulates the nine interconnected ponds which are influential in flood mitigation for the area around the park as it serves as a storm water retention system.
The model produced by Ultimate Flood Consulting can be outlined as:
- Storm water runoff prompts a rainfall hydrograph which will be the inflow of the model
- Ponds acts as buckets for storage if inflow exceeds outflow of the system
- An outflow hydrograph will be produced if the inflow rate greatly exceeds the outflow rate
The flood model created by Ultimate Flood Consulting can be pictured as a simple bucket model; ponds connected to each other by a series of weirs, culverts and pipelines. The nine ponds can be visualized as a series of buckets where flow occurs due to overflow from proceeding ponds concluding through an outlet pipe.
Water Quality Modelling
Ultimate Flood Consulting is in the process of developing a complex water quality model which will allow us to give a detailed analysis of the sediments and pollutants in the Centennial Park water system. Monitoring and modelling of such properties is developed from sedimentation calculations alongside the Flood Modelling completed earlier.
Ultimate Flood Consulting understands the importance of sustainability and assessing and measuring Water Quality is vital to the sustainability of any water based system. Centennial parklands contains a large network of interconnected ponds that act as a semi natural filter to the inflowing urban stormwater runoff, therefore it is important that quality is measured.
Sedimentation transportation is the driver of such nutrients and pollutants in the sediment bodies contained in the water flows. Such Pollutants that will be measured include Nitrogen and Phosphorus.
Similar to our flood model, before development of our water quality model, educated assumptions were made from information provided. These assumptions include:
- Neglecting Evaporation losses for the time period of the model
- Even Dispersion of sedimentation and pollutants as flows enter ponds
- Sediments and Pollutants are not heavily removed by man in any pond
- All ponds have similar base characteristics
- Neglecting excess vegetation removal of sediments
- Concentration of sediments does not decay hence K=0
Conclusion and Recommendations
Although a high level of professionalism and due care was taken by Ultimate Flood Consulting during the project, some errors were unavoidable and may have compromised the accuracy of the current results. These errors are mostly due to the assumptions made above and have resulted due to time and cost constraints of the project in its current stage. These errors can be easily rectified with a more detailed analysis and measurement of the site should the Centennial Park Trust decide to invest further into the project.
Ultimate Flood Consulting realizes these errors have stemmed from the time and cost constraints which have been imposed on us at the current stage of the project, however with the support and approval of the Centennial Park Trust, Ultimate Flood Consulting recommends that the following be done:
- Detailed site measurements to ensure accurate input data
- In-depth analysis of ponds to ensure accurate figures for surface area and volume can be obtained
- Reconfiguring model to add more time steps allowing for more accurate interpolation
- Rerunning the Flood Model Simulator with newly obtain results to obtain a realistic simulation of the behavior of the Centennial park system
- Calculating losses due to evaporation and implementing these numbers in both the flood and water quality models
- Detailed water testing to obtain more accurate figures on decay, dispersion and individual pond characteristics
Ultimate Flood Consulting believes we have developed a flood model capable of simulating the effectiveness of the Centennial Park flood retention system when subjected to heavy flows due to a major storm event. Through these simulations, Ultimate Flood Consulting was able to effectively analyse the system and provide recommendations on improvements based on the findings. With the development of our water quality model underway and with further support and approval of the Centennial Park Trust, we will be able to further refine and develop the models to give an accurate simulation of the system in a major storm event, capable of delivering in-depth information regarding flood management and water quality analysis.
