1 Deterministic Modeling of Culvert Condition

Deterministic Modeling of Culvert Condition / Halifax Regional Water Commission

Halifax Regional Water Commission (Halifax Water) has employed a deterministic modelling approach to create a plan for their storm water assets. The management system was used for long-term planning their culvert portfolio (approximately 1744 cross culverts on 3700 lane km of regional roads). The software uses deterioration curves, a temporal model periodic simulation model and has integrated Geographic Information System (GIS) capabilities.

Initially the analytical objective of the model was to maximize the average condition of all the culverts and minimize the investment. Several constraints were embedded within the initial model analysis including:

  • Non-Increasing percentage of culverts in critical condition
  • Replace all culverts that exceed expected useful life
  • Budget not to exceed scenario

The scenario analysis allowed Halifax Water to establish a minimum investment level required to bring the portfolio to an acceptable average condition state, have a reliable forecast of future condition trends, and quantify an estimate of accepted risk of failures. The figure below shows the agency’s forecasted risk of failure over time based on the selected strategy and projected funding.

NBDTI forecasted culvert conditions using a deterministic model.

Read more in the chapter: 4.3.1 Managing Assets Using Condition Based Management