This is interesting — a very detailed aerial photo of Waikawa Beach from August 1965. Below is only a screenshot, but you can zoom in a long way and with great resolution on the real thing. See it at: Aerial Photograph Print, Waikawa Beach, Sheet 121020 | Archives Central.
Identifier: HDC 00365:2:16
Dated: 07 August 1965. Scale: 3 Chains to 1 inch. Company: Aero Surveys. Negative: 121020. Shows the following features: Waikawa Beach Road, Drake Street, Arthur Street, Manga-Pirau Street
This century note: scale 60.35 metres (3 chains) to 2.54 cm (1 inch).
It’s interesting to note the location of the old footbridge, about 3 properties along Drake Street rather than at the end of Waikawa Beach Road. Also how the river loops back on itself and exits to the sea quite north of its current location — round about where 17 Manga Pirau Street is now.
On the Google Maps screenshot below (not to the same scale) you can see Manga Pirau Street is now a lot longer and has a couple of ‘kinks’ and the position of the river mouth is quite different.
Keep in mind though that the river moves a lot of its own accord. See Aerial photos from the archive. In 1942, for example, the river mouth was down around where the Waiorongomai Stream exits to the sea — about 2 Km south of where it is now.