Key Factors to be Considered for the Proper Design, Construction and Maintenance of Stormwater Inlets and outlets

Auckland's public stormwater network contains more than 120,000 inlets (including about 90,000 catchpits) and outlets. These inlets and outlets play a vital role to the performance of the public stormwater network, as their performance determines whether the surface runoff can effectively enter or exit the system.

Many years of field observation by the authors indicate that the performance of a number of the stormwater inlets and outlets has been a contributing factor in some flooding incidents, mostly due to their design, construction or maintenance. These inlets and outlets have also resulted in land erosion and amenity problems. To minimise these issues in future, a technical report on inlets and outlets for stormwater quality management systems has been prepared to assist in the better performance of these vital assets.

This paper summarises the common but important aspects needing to be carefully considered in the design, construction and maintenance of the following types of inlets and outlets; catchpits, inlets from open watercourses to pipe networks, inlets and outlets of stormwater treatment devices, stream outlets and beach outlets. The aim is for inlet and outlet related flooding, erosion, maintenance and amenity problems to be avoided in the future.