Signs – Please respect our unique coastal areas

Castlecliff Coast Care recognised that the beach area has lots of “Do Not” signage but no informative signs.  As the addition of informative signage is part of the WDC’s Coastal Reserve Management Plan 2018, WDC were approached by Coast Care to work in partnership to create and install suitable signage. 

Four signs were designed and then erected in March 2021, with the theme “please respect our unique coastal areas”.  Each sign has a general information section, plus three sub-panels each of which presents a story about our coastal areas.

Almost serendipitously in the final weeks of the signage project Ian and Jacqui McGowan contacted Coast Care offering  to provide a generous donation to cover the sign production costs.  Further funding was received from WDC to cover assembly and painting.

The signs are located by the Karaka stream, the “brick path” to the beach and alongside the top car park.

Karaka Stream / Wetland

Karaka Stream / Wetland

Banded kōkopu and inanga (Galaxias fasciatus), longfin (Anguilla dieffenbachii) and shortfin eels (Anguilla australis) and occasionally redfin bully (Gobiomorphus huttoni) are found here.

The Stream is fed by clean spring water from the cliff face. Iron sands dissolve in the water causing rust-coloured mud in the feeder streams.

This coastal stream provides a special area for our nocturnal native fishes, having areas for night feeding, daytime shade and suitable spawning areas.

The high density of adult fish spawning in the Karaka Stream suggests many larvae leaving the wetland each year may populate other rivers and streams along this coast.

When Karaka Street and Seafront Road were formed there were no dunes, nor stream or wetland. The beach was just a long narrow strip of sand.
The North Mole collected the sand moving southward in the sea currents so the beach and dunes increased to their present size.
As the beach grew, groundwater emerging underneath Karaka Street pooled at the base of the cliffs.
By the 1930s, this formed a ‘lagoon’ where local children played. Later, the dunes rose in front of the ‘lagoon’, creating a more sheltered environment that favoured the establishment of coastal and wetland plants.
Establishing the beach emergency access roadway and ditch created the Karaka Stream which has developed into a suitable habitat for our native fishes.

This area is home to a population of banded kōkopu,and other endemic whitebait species that are rare in the Whanganui region.
Banded kokopu
• Are scalesless fish.
• Grow up to 300mm.
• Are nocturnal and site loyal.
• They require daytime vegetative cover and shallow, slow-flowing water for night feeding.

Iron sands dissolved in the water are converted by bacteria into iron hydroxide percipitate or ochre, seen as rust-coloured mud, which can combine with organic matter.
This fine black mud is highly valued by Māori weavers who use it to make traditional black dyes. There are only a few paru sites in the Whanganui region.

Castlecliff’s Sand Dunes

Restraining the river mouth with the mole structures results in the sand, which would have travelled further south in the offshore currents, settling and extending the beach by up to two metres annually.

The prevailing westerly winds of this dynamic coast blow the sand inland, building large sand dunes. To prevent loose sand reaching properties on Seafront Road, Australian wattle (Acacia longifolia and Acacia sophorae), and marram grass (Ammophila arenaria) were planted from 1930’s onwards.

In front of these tall unstable dunes there are now lower foredunes that are populated by NZ’s native sand-binding plants, spinifex (Spinifex sericeus) and pingao (Ficinia spiralis).

Castlecliff’s Sand Dunes

Sand dune development between 1929 and today

In the 1939 photograph taken when the freighter Port Bowen stranded close to the beach, the white
breakers are visible. In contrast, today’s view from the same location on Karaka Street is of tall sand dunes covered in vegetation, while the unseen foreshore is much further away from Seafront Road.

Sand dunes continue to build up

These photographs illustrate the build-up of more one metre of sand beneath the Coast Care sign located behind the Duncan Pavilion, in just three years (2010-13). Some sand movement is beneficial to our native sand binding plants, which trap and retain the sand.
However, people, horses and vehicles travelling through the dunes kill plants and disturb the sand.

The result is much increased sand movement that infringes on the coastal infrastructure.

Stay on Paths

A dynamic West Coast Beach

A dynamic West Coast Beach

The Function of a beach is to collect and recycle debris from land and sea.

It forms a flexible and adaptable edge between land and sea, which changes in dynamic ways. Locating infrastructure sufficiently back to allow for these changes is vital.

Sand, a basic element of nature, is found on land and under the sea. Sand is very mobile, particularly on our west coast beaches, where longshore currents deliver new supplies of sand. The sun shines, the wind blows, and the dry sand is carried up the beach to create dunes.

Our ever-changing beach

Sometimes Castlecliff Beach is wide and stable for long periods, with lots of dry sand and logs above the high tide mark. Then storms and high tides drive up the beach, taking the sand offshore, leaving just a narrow beach that may be steep and undulating.
With Castlecliff Beach being close to the Whanganui River, storms deposit both natural and artificial debris on the beach.

How sand dunes rebuild after storms

Storm waves crash onto the beach, dragging the sand offshore and cutting into the dune.

Later, large swells generated by the storm, stir up this sand sweeping it back to the beach edge. In calm weather waves break close in shore, gently stirring up the sand and rebuilding the beach gradually, tide by tide.

After storms the fore-dune native plants’ runners fall down the steep dune edge created by storm waves, quickly repairing the dunes by collecting the moving sand as it travels up the beach.

Spinifex & Pingao

These native sand binding plants, spinifex (Spinifex sericeus) and pingao (Ficinia spirallis), bind and stabilise the sand with their roots.

These foredunes plants are nourished by flotsam and sea spray, which encourages them to grow towards the sea.

Historical Changes to Castlecliff Beach

Between 1908 and 1929 the moles (river retaining walls) were built to facilitate better access for coastal shipping. The longshore currents moving sand southward were interrupted, resulting in a
large triangular area of sand from accretion on Castlecliff Beach.

At times, the shoreline has moved seaward at up to two metres annually. The prevailing westerly winds blow the sand up the beach, creating firstly the low-curved fore-dunes on which our native sand-binding plants, spinifex (Spinifex sericeus) and pingao (Ficinia spiralis) grow. Further inland the tall and steep mid-dunes are formed by marram grass (Ammophila arenaria). These are then colonised with Australian wattle (Acacia longifolia and Acacia sophorae) and karo (Pittosporum crassifolium), plus many weeds and ‘garden escapees’.

Historical Changes to Castlecliff Beach

During the 1940’s defensive structures were constructed around Castlecliff against a possible invasion. A series of pillboxes lined the coastal cliffs, beach front and river mouth.

An arrowhead pillbox can be visited by following a path opposite Bamber Street through the vegetation. This pillbox, built on the foredunes, is now located at least 150 metres from the sea and surrounded by large dunes and rampant plant growth.

Castlecliff Bathhous – Swimming pool filled with sea water at high tide

The bathing house and public conveniences were located close to Seafront Road, between and Manuka Streets. When built in 1919 the concrete facility had a pool in the base that filled with sea water at high tide.

By the time this photograph was taken, probably late 1940’s, sand had built up in front of the building so the tide no longer reached it.

Today, more than 250 metres of sand dunes and beach separate Seafront Road from the sea.

Beach expansion

The coloured lines imposed on this aerial map of Castlecliff show the beach extension seaward. Older residents remember family stories of taking deck chairs across Seafront Road to access the beach and much
shorter walks across the beach for their swims. The lower carpark is now more than 80 metres from the high-tide lines.