Community Involvement, Social Challenges and Daylighting in Water Management, Case of the Ohaku Bay Auckland

Water flooding is an increasing problem in the Ohaku bay. Prior to 1911 Ohaku bay was an area said to drain water easily to the sea. Since the construction of the Eastern Interceptor of the Auckland Suburb Drainage Scheme the situation has changed, as it allowed the main sewer pipeline to be laid across the beach. With the height of 2.59m and the location in a low-laying land the internal pipeline as well as the construction of Tamaki Drive has created a situation which stifles the water from finding its way to the sea and hence has raised the ground water table making it susceptible to floods. Currently there is a Maori burial ground on the site, and it is said that the community faces issues during burial etc., due the higher water table. 

It is expected for this location to develop more floods in the near future if the situation remains the same. This is due to the climate change, rising of sea water and the increase in extreme weather events including rainfall intensity. To resolve this problem, an investigation has been undertaken taking into consideration the community involvement which recommends the removal of the culvert and replacing it by a water channel of a 6m width and 6:1 batter slopes. The water channel will have more benefits to the environment as it provides the area with freshwater as well as marine life.

The analysis of the proposed water channel put forward a maximum flow rate of 3.4m3/s. This is close to meeting the requirement of a 2 year storm event. This investigation will provide the history and the present situation of the area, the previous effects of the culvert and the road and the expected effects on the future. Furthermore, this search will discuss options and provide a suitable solution and the methodology needed for the construction of the solution. Additionally, the study will deliver further details on the channel, the effect of tide on the channel flow, transmissivity, habitat creation as well as streambank vegetation.