Markov Model for storm water pipe deterioration

Effective management of storm water pipe networks requires an accurate assessment of the structural condition of the pipes. Indeed, the recent introduction of Australian accounting standard AAS27 compels local governments to prepare annual financial statements,including the depreciated value of their storm water network. A rational approach to assessing depreciation is to base it on structural deterioration. This study presents a Markov model for the structural deterioration of storm water pipes. The model is calibrated, using Bayesian techniques, to structural condition data from the storm water asset database of the Newcastle City Council (Australia). It is shown that the Markov model is consistent with the data. The pipe characteristics of diameter, construction material, soil type, and exposure classification were found to influence the deterioration process. It is also shown that the depreciation methods required by AAS27 significantly overestimate the structural deterioration.