Environmental Effects at Pegasus Bay

Why is Pegasus Bay sandy?

The cause of the sand build-up is the natural shape of the coast. Banks Peninsula acts as a large shelter for Pegasus Bay. The peninsula causes the sea current to form a large eddy (circular motion) in Pegasus Bay, causing sand to accumulate. It also protects the bay from the southerly storms and prevents the northward movement of sand up the coast.

20,000 years ago the shoreline of Pegasus Bay was 50 kilometres further out to sea and 130 m lower. As the climate warmed and cooled over time, the continental shelf was continually flooded until the shoreline became stable at its current position about 4,500 years ago. This means that the coast as we know it – its landforms, estuaries and sediment, is relatively young.

Much of Pegasus Bay is open flat beach area backed by extensive dunes. The dunes need to be eight metres above mean sea level to be effective against storms.

Sand dunes protect the land from the forces of the sea during storms. Without healthy sand dunes, settlements along Pegasus Bay could be threatened.

Facts about sand dunes:

Sand dunes are a natural barrier that protect the land, development and entire settlements from coastal flooding.
Sand is washed onshore and offshore by waves which surge up the beach carrying sand particles.
Without plants growing in the dunes, the sand would be carried away by the wind.
Dune plants are called ‘sandbinders’ because their long leaves are shaped to trap the sand when the wind blows it around. The dunes build up and the plants grow higher and their roots get longer to act like an anchor in the sand.
Dunes provide habitats for native plants, birds and animals.

Issues

Impacts of vehicle use

Anecdotal information and observations indicate an increasing number of recreational vehicles (4wd, 4, 3 and 2 wheeler bikes) accessing the beach areas of Pegasus Bay. It is accepted that a large number of these are using access for low impact purposes such as getting to fishing and whitebaiting areas and for launching and recovery of craft. However, there are other groups and individuals that use the beach, and the dune areas, for recreational driving. Again, a large number of these are reasonably responsible but the issue stems from two factors:

Use of the coastal area by growing numbers of vehicles in ignorance of particular values or the needs of other users;
Use of the coastal area by vehicles driven in an anti-social and aggressive manner and also vehicles which did not meet the legal standards required (for the purposes of safety the beach is subject to road regulations).

The principal issue contains a number of sub-issues:

Conflicting uses
Vehicle/pedestrian
Boating/fishing
Vehicles/natural values such as flora and fauna
Human use/damage to dune systems
Legal use/uncontrolled potentially illegal use
Concentration of vehicle impact in ‘favoured’ areas such as Ashworths Spit

How do people affect the coast?

Sandy beaches attract people for a number of reasons...

Recreation

Development

Services

Walking, playing on the beach, walking dogs, fishing, horse riding, surfing, 4 wheel driving, jet skiing, boating.

All these activities require people, animals or vehicles to move across or near the coast.

They could disturb nesting birds or destroy plants that grow on sand dunes.

Building housing for permanent or holiday homes, businesses, structures built right on the coast such as jetties or sea walls.

These activities may attract more people for recreation. Structures built on the coast could interfere with normal coastal processes.

Port operations, sewage outlets.

Ships and other sea vessels may contribute to marine pollution.

Population growth near the coast means an increase in sewage discharge. This could lead to contamination if not treated correctly.

Northern Pegasus Bay Motor Vehicle Access Strategy

The strategy contains recommendations on whether or not vehicles should be allowed to access beaches on the Northern Pegasus Bay coast between the Waimakariri River mouth and "The Rocks" north of the Waipara River.

It is a non-statutory strategy, which means its recommendations are not binding until the four organisations who look after this coastline (Environment Canterbury, Hurunui District Council, Waimakariri District Council and the Department of Conservation) agree to adopt the strategy and its recommendations.

Christchurch City beaches are already restricted to vehicle access.

Coast

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