There is a road that goes from Titirangi all the way to Whatipu which is the beach on the North side of the Manukau Heads. On the way you see the Upper Nihotapu Dam
Nihotapu is pronounced Nee – hoe – Tap – u (like in poo) It is the Maori name.
Here is the enviromental visuals from this dam.
To get to Nihotapu Dam and there it is at the bottom of a very steep long hill after passing the Langholm turn off.