Disappearing beaches: saving our beaches

by Dr J Floor Anthoni (2000)
Because beaches and dunes change very slowly, humans do not notice what is happening. Because they also poorly understand how dunes and beaches behave, they often do the wrong things. Here you can learn how to detect if a beach is healthy or sick, what causes it and what you can do about it. But not all beaches can be saved. 

symptoms of a sick beach
Learn to recognise the symptoms of a sick beach. Every beach is different, has different threats, a different history and needs to be treated differently. 
threats to our beaches
Almost all the threats to our beaches come from human activities, often far away from the beach. We somehow need to change our ways and behaviour.
what we could do
Not all beaches can be saved but it is important to recognise which can. Using local examples, seemingly outrageous suggestions are made.
beaches worth saving
A review of some beaches in northern New Zealand, that are worth saving. The examples may illuminate general considerations.
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Symptoms of a sick beach
Disease symptomsAs we have set out extensively before, the health of a dune/beach system has little to do with the amount of sand either in the sea or on the land. So one does not need to spend decades of laborious monitoring of the sand budget in order to qualify the health of a given beach. (In fact sand mass monitoring does not say anything about beach health at all). But some knowledge of a beach's history could serve to advantage, much like a physician takes clues from a patient's history. 

Just like patients, no beach is alike. They are physically different, and are affected in different ways by the same causes. So a bit of detective work is needed before embarking on a course of action or before drawing a final conclusion. But in the main, almost anyone can now assess the health of one's own stretch of beach.

Dunes and beaches grow and shrink cyclically, depending on climate cycles and other cycles. Although the amount of sand in the dune/beach system can vary considerably, our health indicators remain valid whether the beach is growing or shrinking.

Contrary to rocky and sandy cliffs that cannot repair themselves and therefore can only shrink, beaches can hold their own over many thousands of years.

The picture shows a short-hand checklist which we will examine in detail below.

Threats to our beaches
Threats to beachesNot surprisingly, the main threats to our beaches arise from human activity. The drawing shows the most important ones, which we will summarise here from right to left:
Because the demise of our beaches is directly linked to human activity, today's problems are likely to accelerate in the future. The economies of societies expecting to become wealthier each year, grow annually between 3% and 6%. Growing at 3%, our problems will double in 25 years and quadruple in 50. Growing at 6% will quadruple our problems in 25 years and four times again in the next 25! Extrapolating this scenario implies that all our beaches will eventually die.

Because the health of our beaches is so intricately entwined with everything we do, it seems almost impossible to salvage them.  Is there anything we could do?

What we could do
Destined to destroyWhen asked, people do like their beaches. They are just not aware that their daily actions destroy the very things they like. Many of our actions do not only destroy beaches but also to a larger extent, our terrestrial and marine environments. Obviously, our societies will need to make major environmentally friendly adjustments. All over the world, environmental groups are championing this cause. It will take time and public education. 

But what could we do immediately? The following suggestions seem outrageous because they go against established beliefs and well intentioned effort. Remember that each beach has its own problems and remedies and that some beaches cannot be salvaged at all. 

Examples of beaches worth saving
Using the information presented in this section Our disappearing beaches, everyone should be able to assess which beaches are worth saving and which ones can best be left alone. You will be able to determine when a sea wall is the only remaining solution left. It would of course be impossible to do a review for the whole of New Zealand here, let alone one for the entire world.

Let's start with a popular beach which is beyond rescue, Orewa Beach, just north of Auckland, New Zealand. Houses and trees are too close to the water's edge, the beach lies flat for many hundreds of metres, soil erosion is vast, sewage from the population of 30,000 is released nearby, the beach sand is polluted and the sea has progressed too far. For Orewa the only protection remaining is a sea wall. This sea wall could be constructed anywhere up to 500m in the sea, reclaiming land for a buffer zone, but it would diminish the value of local property if what remains of the beach is moved further away.

Note that Orewa beach may well be a good candidate for beach dewatering applied in several stages. Dewatering allows the sand to dry and blow towards the present wall, creating a dry beach zone. The amount of sand can be controlled by turning the pumps on or off, such that the right amount of mobile sand is created, not to blow onto properties and roads. During storms the dry beach will disappear but it will rebuild rapidly due to dewatering.

Orewa Beach at low tide
Orewa Beach at low tide during very calm weather, shows how flat this beach is. The sand can no longer dry. Houses encroach right to the water's edge. There are rows of tall trees and tall buildings. It would economically not be possible to restore the sea wind but dewatering is an option.
Orewa Beach during rough weather
Orewa Beach just before low tide during rough weather, shows how far the shallow sand and sand banks extend into the sea (about 500m from the high tide line). It is where all the sand of the beach and all renourishment efforts, have gone.
Orewa Beach at high tide
Orewa Beach during high tide shows the water lapping at the boundary of private properties. Along most of the water front, the local council has erected sea walls. After breakers have crossed the vast stretch of flat sand, they have lost nearly all their energy. It makes people believe they are safe here, but they are not protected against storm surges.
Polluted sand of Orewa Beach
The beach sand of Orewa Beach looks polluted by fine particles (silt and clay) and it never dries. Erosion from urban development and roading and sewage from the local sewage treatment plants, end up in the sea.
Plan for Orewa's beach centre
A drawing from recent plans for renovating Orewa's beach centre. The three steps in the foreground are the only barrier between the city and the sea. At the other end of town, engineers are constructing a sea wall with entirely different proportions (see right). The coastal area has not been zoned by hazard rating. Property owners do not know the risk of living or building here.
Building a sea wall at Orewa
After winter storms in Nov 1998 had carved some foreshore away, it was decided to construct a sea wall there. The design involved a ditch of about 1m in the beach sand from which a plastic, permeable cloth (geotextile) slopes up the shore. The whole is covered in large boulders. The cloth is supposed to hold back the sand while letting ground water and storm water through.

Otama Beach on the Coromandel Peninsula, New Zealand, is an example of a pristine pocket beach that somehow has escaped development. It is backed by a wetland reserve and is a prime candidate for a pristine dune wilderness area, fronted by a large marine reserve.

Map of Otama Beach
Otama Beach is a pocket beach strung between headlands, facing north. It is very exposed. The peninsula is sparsely populated and produces relatively little run-off. The waters are clear most of the year. The beach is backed by a wetland nature reserve and the Otama River has a small catchment area. The beach reserve should enclose the entire catchment area and ocean extending to 40m deep.
Otama Beach, Coromandel
Otama Beach has all the symptoms of a healthy beach: glistening clear quartz sand that squeaks when walked on , a gently sloping fore dune which is sparsely vegetated by the native spinifex dune grass (Spinifex hirsutus), while mid and rear dunes are low in profile. There are no houses.

Beaches worth savingIn the northern part of the North Island, New Zealand, I have earmarked a number of beaches that are worth saving first. The accompanying map shows where they are. Each beach is worth saving for a different reason. It is of course impossible to be complete but everyone knows a beach in his/her locality that is worth saving first. From the Otama Beach example and the examples below, a number of reasons and conditions become evident. By focussing effort on those beaches that are still in a salvageable or even healthy state, quick progress can be made, while the result is also likely to remain successful.
Map of Parengarenga Harbour, NZ.
The Parengarenga sandspit (Kokota) must be preserved as a dune/beach reserve. 
Parengarenga spit, NZ
Parengarenga Harbour is the northernmost harbour in NZ. Its sand spit consists of almost pure quartz sand. It is sparsely vegetated and its sand can wander freely.
Karikari Bay
Location of Puheke Beach and Karikari Bay on the Karikari Peninsula. Bottom centre is the Rangaunu Harbour.
Puheke Beach
Puheke Beach showing dunes and vegetation. In the top right corner Mt. Camel, guarding the entrance to Houhora Harbour.
Map of Hokianga Harbour
The tall Hokianga Harbour dunes on its northern spit have been planted estensively in pine forests. The wild bare dune is worth saving as a dune/beach reserve.
The Hokianga harbour and tall dunes.
The Hokianga Harbour with its entrance on left behind the rocky promontory. The unique wild and tall sand dunes are threatened by pine plantations in the far distance and they are shrinking.
Map of Bream Head with Ocean Beach
Ocean Beach is found on the ocean side of Bream Head, a sparsely populated peninsula. A dune/beach protection reserve could be combined with a marine reserve rounding Bream Head and extending into the harbour entrance.
Ocean Beach near Whangarei, NZ
Ocean Beach extends from an easily accessible bay (behind us) past an inconvenient headland, into the far distance. On left a tall rock face but in the distance low profiled dunes and a steep beach with clean sand.

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