Modelling Stormwater Pipe Deterioration

Stormwater pipe networks, as with other forms of buried infrastructure, are extremely expensive to develop and maintain. These high costs demand that an accurate evaluation of their current structural condition is essential for their effective management. This study presents a Markov model for the structural deterioration of stormwater pipes. The model is calibrated, using Bayesian techniques, to structural condition data from the stormwater asset database developed by Newcastle City Council (Australia). It is shown that the Markov model is consistent with the data. The pipe categories of diameter, construction material, soil type, and exposure classification were found to influence the deterioration process. The introduction of Australian Accounting Standard AAS27 compels Local Government to determine the depreciated value of their stormwater network. A rational approach to assessing depreciation is to base it on structural deterioration. It is shown that the depreciation methods required by AAS27 significantly overestimate the structural deterioration.