Historic Shorelines

This dataset contains a number of historical shorelines mapped from surveys and aerial photographs. Data is available at a number of locations around the Waikato Coast, with more data in areas with development at risk from coastal erosion. Data collected for evaluation of historic shoreline change and coastal hazard evaluation. Early datasets were digitised from registered hard copy plans and photographs for use in hazard assessments in the late 1990s. More recently, historic shorelines have been digitised from orthorectified historical aerial photography with greater coverage.

1. Lines showing Historic Foreshores containing attributes stating year of survey, survey plan and shoreline type (toe of dune, edge of vegetation, MHWM, MSL etc). 2. Lines and areas showing Historic Shoreline Erosion containing attributes stating year of survey, survey plan and erosion type (blowout, storm scarp, mound or seep) More recently collected data is available in GIS layers with details of location, date and source. Coverage includes a complete shoreline digitised from 2012/13 photography, as well as historic and more recent shorelines in areas where there has been measurable change (mostly soft shores), including (this list may not be comprehensive): - 1940s (all soft coast) - 1950s: Opoutere/Wharekawa, Whangamata, Port Waikato, Raglan, Aotea, West Coast (parts). 1959 Southern Firth of Thames and Whiritoa. - 1960s: Port Waikato, Raglan, parts of West Coast, Aotea, Kawhia, Awakino, Mokau, Whangapoua (upper estuary), Whiritoa, western Firth of Thames. Tairua, Pauanui, Whangamata and Wharekawa. Kennedy Bay and Matarangi/Whangapoua. Whitianga area. - 1970s: all Coromandel Peninsula, most of West Coast, some of coast more than one record. Mokau and Awakino. - 1980s: Coromandel most sites, Kaiaua/Miranda coast, West Coast (Aotea, Kawhia and parts of southern coast including Awakino and Mokau) - 1990s: southern areas of Coromandel Peninsula (both sides), Firth of Thames, West Coast (incl. Aotea) - 2017: where coverage available, including many sites on Coromandel Peninsula. Not full regional coverage.

Waikato Region

Shoreline records from as early as 1850s through to present.

The hard copy plans were scanned and registered using underlying CRS parcel data. The ability to register accurately was limited by the amount of parcel data on the maps. Registration was ‘best fit’. Lines were then digitised and attributes populated. Some of the plans were compilations of survey records specifically drawn for the Council to show several years of historic shorelines. Shorelines digitised from historic orthorectified imagery, at scale of 1:5,000 - 1:8,000. Quality of imagery varied and scale of mapping varied accordingly. Mapped in more detail in key areas.

See method above. Data collection ongoing as photographs become available. Data quality: Shorelines from surveys based on hard copy plans. As all plans are of survey quality it can be assumed that the foreshore definitions are to the same standard. Some of the plans weren’t very clear in areas where several historic shorelines crossed each other particularly because of them being in black and white. If absolute accuracy is required it must be obtained from the underlying survey plan. Shorelines digitised from orthorectified photography - accuracy dependent on scale and quality of imagery. Dataset generally is particularly focused on areas where development is threatened by coastal hazards, and/or where the shoreline is changeable. Most data is therefore available for the sandy beaches of the Coromandel Peninsula, and River mouths on the West Coast. Cliffed shorelines have not been repeatedly mapped where there is no measurable change. Recent work has considerably widened the coverage of the shoreline mapping.

Data is available in hard copy maps to be viewed at Waikato Regional Council. All data is also available electronically in most GIS formats.

Assessment of coastal hazards and development of coastal hazard policy.

Data available from Waikato Regional Council. Some data available for viewing through the Waikato Region hazard portal (see below). No confidentiality.

Data collection is ongoing.