Richmond, the largest town in the Tasman District, has a central area that lies at the confluence of two stormwater catchments. While there are detention dams upstream designed to protect the town centre, the stormwater systems do not meet the current desired levels of service and the town centre experiences periodic flooding.
In April 2013 a severe (1 in 500 year) rainfall event caused widespread flooding in the town centre which re-focused the community and the Council on the stormwater deficiencies and reinforced the priority to upgrade the stormwater infrastructure.
The proposed $13.9 million solution, is a major staged infrastructure project to improve the flood protection while also taking the opportunity to improve the accessibility, safety and functionality of the main street. As part of the initial stage, as well as upgrading the existing stormwater pipes, the crown of the road will be lowered to prevent floodwaters flowing towards business entrances, as happened in 2013. The surface of the street will be reinstated and the community invited to contribute ideas towards the design.
The second stage involves a new 1600mm dia. pipeline to divert stormwater flows away from the Richmond central area out to the estuary via a new widened open channel drain. The new pipeline will collect flows from one of the upstream detention dams and other upstream diverted stormwater pipes.
Subsequent stages in the 10 year programme include further upstream diversions and improved management of overland flow paths.
This paper presents the flooding issues, options considered, the selection of the preferred solution and highlights some the challenges encountered during the design of the first two stages.