This historic place was registered under the Historic Places Act 1993. This report includes text from the original Proposal for Classification considered by the NZHPT Board at the time of registration. The Waihao River Outlet Box is a purpose built water outlet and tunnel for conveying water from the Waihao River to the sea to prevent flooding of surrounding farm land. An earlier outlet box, located 1.5 kms north of the present structure was washed away in 1908 and the present outlet box was built in 1910 to the design of F. W Marchant. The box is an innovative response to a local problem and continues to serve its original purpose. An interesting engineering structure, it is thought to be the largest water outlet of its type on a New Zealand river.