The Lower Manawatū Scheme (LMS) covers a vast area, including:
The stopbanks along the Manawatū River near Te Matai Rd between Palmerston North and Ashhurst are rated for a 1-in-100 year flood. These stopbanks protect more than 360 hectares of agricultural and horticultural land, as well as homes and businesses. However, the awa was slowly eating away at the riverbank near a bend in the river, getting closer to the stopbanks.
The scope of work was to try to deflect the river around the bend in a way which was not going to cause erosion. We achieved this by placing 440 metres of armouring rock (riprap) along the true right side of the river. This effectively tied together two existing sections of armouring further up and down the river. We are also upgrading a section of stopbank in this area. Construction began in November 2022 and was slightly delayed due to cyclones Hale and Gabrielle. This project was largely completed towards the end of 2023.
Hartley St in Foxton Beach faces the Manawatū River very close to the river’s mouth. It is a dynamic section of the awa due to tides in the area. It is not uncommon for river levels to get so high the nearby carpark at the Manawatū Marine Boating Club floods. An existing rock wall along a section of Hartley St was replaced with an engineered rock lining. The work was a natural progression of the work Horowhenua District Council did beforehand to maintain and upgrade the damaged boat ramp just downstream.
This project was a good example of the social procurement goal of these projects. During the construction, local contractor Alan G Gibson was able to provide one of their employees the opportunity to advance their machine operating skills with exposure to the rock placement work.
The LMS includes more than 20 kilometres of stopbanks protecting livelihoods between Tokomaru township and the confluence of the Tokomaru and Manawatū rivers. While many of these stopbanks are out of the public eye, they are a key asset in the LMS. Several sections of the stopbank were at risk of erosion due to their ‘skinny’ geometry. We mitigated this risk by strengthening and reshaping the stopbanks to the correct height and width, which will improve resilience during peak flows.