2019 – The Long-Term Performance of Seepage Improvement Works at New Zealand Dams and Canals

Don Tate

Failure modes of seepage and internal erosion have been identified as one of the key issues for the
ongoing safety of dams and canals in New Zealand. Accordingly, many dams and canals have had
improvement works carried out to mitigate this issue. This paper examines the long-term performance of these measures including three case studies. It is concluded that the performance of these measures has been variable, but ongoing monitoring and periodic review has identified deterioration in performance. There are a number of technical areas where uncertainties on long-term performance may still remain, such as geotextiles in important filter functions and waterstops of various types.