One of the ways you can investigate is visiting 9th Century Black Maps - Check out that huge lagoon and wetland that used to be where Washdyke industrial area is today... you can also see the Waimataitai wetland that used to be at Ashbury Park and the changes at Otipua Wetlands too! https://www.arcgis.com/apps/webappviewer/index.html?id=bec5eceea7514735b73bbe9e8082371f