Model Decisions: Cost-Based & Value-Based Stormwater Infrastructure

By Yekenalem Abebe, Dr. Solomon Tesfamariam 06:59AM September 24, 2018



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Stormwater drainage systems are our first line of defence against pluvial flooding. In recent years, many Canadian studies have pointed to the abysmal state of our current stormwater assets and the fact that those drainage networks, designed based on historical climate regimes, may be defunct due to climate change.

Solutions to determine the most cost-effective way to adapt Canada’s stormwater drainage systems now and into the future are needed.  

In response, a research team out of the University of British Columbia is developing a System Dynamics model coupled with GIS capacity to capture the management process. This will allow for the evaluation of the current and future condition of asset components and allow for the planning of appropriate interventions to improve the overall performance of the stormwater systems.

Deconstructing a stormwater system

Stormwater drainage systems are composed of multiple components, such as sewer networks, retention ponds, wetlands, and swales, that are geographically distributed and interdependent. Different municipal departments are usually responsible for managing these assets. All of these components are expected to function based on their intended design capacity over the planning horizon. However, they may fail to due to so as a result of environmental, physical, and operational factors affecting their performance. For example, metallic pipe corrosion could lead to pipe breaks, or silt can accumulate in infiltration trenches, reducing the hydraulic capacity of the system. Therefore, to maintain the required level of service and meet overall stormwater management objectives, an effective asset management system is crucial.

Planning for future costs

In asset management planning, the owner’s ultimate goal is to generate a set of maintenance and investment actions to optimize its objective function over a planning horizon. To establish a set of optimized actions the owner has the option of using a cost-based or value-based approach. In our research, we have proposed a holistic asset management framework that combines both cost-based and value-based objective functions in the decision-making process. The approach brings a single, unifying framework to investigate all asset components and their interaction in the management process. 

The model is divided into three modules:

  • The sewer network (pipes, manholes, and inlets/outfalls)
  • LID technologies (storage, infiltration, and filtration)
  • Open channel flow routes (gutters, culverts, and ditches) 

The modules are being developed in collaboration with multiple municipalities from the Okanagan Region and are expected to be completed next year. Model validation is scheduled to take place this autumn using data collected from our partners. Respecting the many differences between one municipality and the next, the model can be adapted to the local context and implemented anywhere. When completed, the tool will help municipalities to make network level decisions, specifically, it will assist in:

  • Assessing maintenance needs to keep the required level of service;
  • Investigating alternative maintenance strategies;
  • Estimating operation and life cycle cost; and
  • Assess cost covering tariffs.

Asset management is a systematic and cost-effective process of maintaining, upgrading, and operating physical assets. Further research in the area is crucial to improving current practices in stormwater assets management.

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