Beach profile monitoring
Beach profile monitoring is usually undertaken as survey transects running shore normal from the dune to the low water mark. It provides information that can be used to assess whether a shoreline is eroding or accreting.
You can view where regional councils monitor the beach using Coastal Explorer.
What is beach profile monitoring?
Beach profile monitoring is usually undertaken as survey transects running shore normal from the dune to the low water mark. Sufficient measurements of elevation and distance are taken along the profile to accurately establish the profile cross section. The survey profiles are registered back to a survey bench marks on the ground (often in the sand dunes and safe from erosion) and some survey datum, although with modern GPS based survey systems the bench marks can be virtual. The measurements are undertaken on a regular basis often at monthly intervals, although in some cases these can be infrequent as 6-monthly or annual, and maybe after storm events. The spacing between profiles and the frequency of surveying depends amongst other things on the type of beach, the reason for collecting the data and financial constraints.
The profile measurements are sometimes supplemented with more frequent distance offset measures made from a bench mark to the dune toe, shore parallel surveys along the dune toe or high water mark (usually using a DGPS survey instrument and quad bike), fixed aspect photographs of the site, aerial photographs and wave and current observations by observers at the time of the profiling.
In New Zealand it is typically Regional Councils that conduct beach profile monitoring programmes. Beach profile monitoring provides information that can be used to assess whether a shoreline is eroding or accreting on a long term basis, the amount of erosion and cut back of beaches during storm events and how the beach recovers after those events. Augmented with other coastal process information they provide essential information for coastal management including monitoring the effects of sand extraction on the shore and designing coastal hazard setbacks.
Viewing the location of beach monitoring sites using Coastal Explorer
At present there is information on monitoring programmes from 6 councils available from Coastal Explorer.
An explanation of how New Zealand beach types are classified and mapped and how the different beach types and their associated hazards are identified.
What is beach type?
Beach type refers to the prevailing nature of a beach, including the waves, tides and currents, the extent of the nearshore zone, the width and shape of the surf zone, including its bars and troughs, and the dry or subaerial beach. The beach types that occur around the New Zealand coast are products of the forcing by waves, the tide range, beach morphology and beach sediment characteristics.
The hazard rating for beaches
There is a beach hazard rating associated with each beach type for the most commonly occurring (or modal) wave conditions. The beach hazard rating takes into account hazards such as rips, surf zone currents, deep water and holes nearshore and how changing breaker height affects the hazard rating for each beach type. Currently some 270 New Zealand beaches have been classified and assigned a hazard rating.
The classification and mapping of beach types and hazards
The classification and mapping of beach types involved identifying modal wave conditions (breaker height), tide range and beach morphology (the configuration of sand bars, and rip channels, beach slope) and sediment characteristics (grain size). This was carried out by undertaking site visits to numerous beaches throughout New Zealand, supplemented with information from literature search, aerial photographs and using numerical models to generate tide and wave information.
An assessment of beach hazards as they relate to water safety was also conducted during site visits. This identified hazards such as rip currents, submerged rocks and reef, stream mouths, along with features that influence the level of risk associated with the hazards, such as the type of access to the beach via tracks or road and facilities at the beach such as Surf Life Saving Clubs and public toilets.
The mapping began as a collaborative project with Professor Andy Short of the University of Sydney and capitalised on his 17 year effort mapping, classifying and applying hazard ratings to more than 10,000 Australian beaches. In addition mapping undertaken of additional beaches by Surf Life Saving New Zealand was assimilated into the database.
Beach characteristics and hazards can be viewed for each beach as beach report cards on Coastal Explorer.
Note: WRENZ is currently unavailable because of technical problems as a result of a google maps API change.
On entering Coastal Explorer the user can zoom from a map of New Zealand to a specific point of interest, and mouse-click on a point to access the Metadata for the record viewed via the info (or information) windows or boxes. The Metadata gives the location, the record duration and the frequency of profiling along with the name of the agency that holds the information.