Tuesday, October 7, 2008

Welcome Eastbourne Spring

Monday 6 October was a day to go for a gentle walk along 'The Bays' foreshore and up in the bush above Lowry Bay. Over the last year residents of Lowry Bay and Point Howard along with much work from the Wellington Regional Council have cut a magnificent new walking track from the top of Cheviot Road up to the parking area near the Point Howard Playcentre. On the way I captured several little gems . . . . .

Metrosideros carminea on the
driveway bank at 38 Mahina Road

Coprosma repens nestling on an

exposed costal rock Mahina Bay

Lichen on the rocks (1), Mahina Bay

Lichen on the rocks (2), Mahina Bay

Foreshore beauty
(can anyone give me the botanical name?)

On a rock just south of Whiorau Reserve sat some Shags

Moving up into the bush in Lowry Bay,
the new track is a pleasure to walk on.

Near the top of the track one gets a magnificent
view of some Clematis
on an old large Rata tree.

Walking back along the foreshore
a tanker is
seen being lead to the
oil-wharf by its little minder.

The next day the sun had gone and
the tanker left again in a violent storm.

Have a great day!

Sunday, October 5, 2008

Days Bay Seawall Debarcle - more photos.

A while back ( a year?) the Hutt City Council decided to put in more Post & Board seawall on the Days Bay beach. However the southerly storms we have experienced this winter (2008) seriously undermined it and exposed the fact that the engineering design was totally inadequate. No account had been made for the fact that the 'seawall' was planted in sand. There is much more about this in earlier posts. This post simply publishes more photos of the latest wall being constructed where the old(new) wall was torn out.

Digging out the last of the 'old' posts.

Waste posts!
Placing new posts
A completed line

Pile foundation - deep excavation was
undertaken and
44 gallon drums placed
so the sand wouldn't collapse
the post before the concrete is poured

The first section of the new wall 'completed'. When this photo was taken the flat capping board had not been strapped down - it was simply 'gun nailed' in place. If it is not strapped it will be easily lifted off in the future by the action of the waves throwing weighty debris up underneath it as happened with the last wall.

Let us hope that this wall does what is required of and that it lasts. For the ratepayers sake we also hope that the engineers undertaking the wall design had good insurance. We'll watch progress on this one and report occasionally.

Beach scapes - old and new

This post presents several photos of the Days Bay beach from 1987/8 and also 2008 - approximately 20 years apart. This is a very short time frame for looking at beach erosion and replenishment. However, one of the interesting things is the relative lack of sand on the Days Bay beach 21 years ago and it illustrates how the sand comes and goes.

The photo below was taken in 1987
This photo was taken October 2008
The photo below was taken 1987, before the EBC
undertook remedial work.

This photo was taken a year later - 1988, after the EBC
had done sand replenishment and Pingau planting.The Council also extended the storm water pipe
by one length of pipe as it was thought the
stream outflow
was also contributing towards erosion.
Note the height of the sand where the pipe
leaves the bank. Photo 1988
The next photos were taken at the beginning of October
. The top photo is of the new 'replacement' wall.
The extra length of pipe placed in 1988 has been removed.

It is possible that the presence of more shingle on the Days Bay beach today is simply a removal of sand exposing older gravelly material rather than new deposits brought into the harbour by the action of the southerly storms. This is given some weight when one looks closely at the colour and type of coarse material showing up. It has considerably more brown coloured material than the hard grey rock being brought in to the harbour from the south.

Friday, October 3, 2008

Days Bay Seawall Restoration

Sandy beaches come and go. More so if they are on exposed coast lines. But Wellington harbour, with the harbour mouth facing south and the receptacle of stormy weather, also presents a challenge to those who would tame the sea.

Despite the harbour having a relatively shallow entrance that breaks the ferocity of the southerly storms, the eastern side of the harbour has continually taken a beating from the sea. The southerlies take material from the beaches and can also deposit new material from outside the harbour entrance on the foreshore.

This eastern side of the harbour has been subject to interesting changes over the last 150+ years. 160 years ago Days Bay beach was a swamp. Then a large earthquake in 1855 lifted the shoreline by 1200 – 1500 mm. That enabled a road to be formed where previously it was impossible. Prior to that the sea had relentlessly, for some hundreds of years, tickled away at the foreshore taking bits off here and there and depositing sand in other places. Most of Eastbourne village is built upon old sand dunes. In the 1950’s houses were literally being tipped into the sea at the southern end of Eastbourne. Millions of dollars were poured into the sea in the form of land protection work to maintain the values of the beach front properties, until the 1980s, when another piece of natures work surprised us. But more of that later.

Days Bay beach has long been popular – even before there was any good sort of road, or good road transport for day trippers and picnickers. But the increased use of cars in recent times and the need for more parking along side the beach in Days Bay for day ferry commuters, combined with the apparent need to protect the edge of the road from erosion, has lead to attempts to “hard edge” the contact line between sea and land. On sand this is extraordinarily hard to accomplish with success. Many years ago a small wooden retaining wall, on the northern side of the wharf, was erected. That has been largely successful to date, possibly because it is partially protected by the wharf structure and somewhat still in the shelter of the southern point of Days Bay.

Then a little bit more wooden retaining was put in. That has also been largely successful to date. (Small remedial action on both walls has had to be undertaken.) Remember though, we are talking a few years – not the time frame that sea erosion works to. Those sea forces might rip out yesterdays’ wall and then it might take 70 years or 100 years for the wind and wave direction etc to be such that it undoes mans’ best efforts. It is interesting to note in the photographs that while three palings are exposed at the southern end (in front of the Boat Shed), at the northern end four and half palings are exposed above the sand. The tops of the concrete foundation for the retaining posts are also becoming exposed. The beach is lower at the northern end, shown below.

The photo above shows the join of the third section of seawall. This is lower than that it joins and in this photo shows about one and a half palings above the beach level. Further north, showing in the following photo, two palings are showing. The beach is being lowered the further north along the beach one looks.

So then the Hutt City Council decided to be brave or foolish and further extend the wooden wall. It would ‘tidy’ the area, provide more parking and also allow the addition of a narrow walking track that was not there before. But that part of the beach is more exposed to the southerly wind-whipped sea. The beach is lower at that point (than further south) because of that greater exposure. Consequently the wall was a little higher than along by the wharf. This recent short winter the new wall was effectively wiped out. Undermined.

The photo below shows the recently installed walls being removed. Apart from very shallow footings other aspects of the construction were poorly designed. Gaps between the palings allowed erosion of the cloth backing and removal of the infill behind, by the sea. The wall capping was only held down onto the posts with 150mm stainless nails. In parts the thrashing by the sea (including floating logs) lifted that capping, simply pushing out the nails. The capping should have been held down by stainless steel strapping.

The first finger pointing must be at the engineering design. In Eastbourne there are now enough ‘lay engineers’ who could have told the council that if there was any hope of the wall surviving in sand it would need a very deep foundation. On a rocky shore line a footing would need to be excavated below the upper rock level to allow for some erosion. All along the Eastbourne coast line there are again examples of poor engineering design and poor implementation of wall construction. The photo below is a pile of piles! These have been dug out following the design failure.

I produced a series of photographs in the early 1980s along the marine drive to Eastbourne of the many failing bits of seawall at that time. That resulted in considerable seawall upgrading and considerable learning on the part of the people involved. That learning has unfortunately apparently been lost and design and installation workmanship deteriorated. More recent seawall ‘enhancement’ now has many wall ‘foundations’ hanging in mid-air with the loose material they were seated upon washed away. This can be seen in Mahina Bay and Sunshine Bay. The last couple of weeks has seen the most recent board wall in Days Bay totally removed and being replaced with a much deeper foundation. Appalling original design or construction oversight. I wonder if the new one will survive?

The problem now is likely to be that this greater height of seawall will lead to the flattening of the beach during storms to an even greater extent and make the wave attack on the beech and wall that much greater. Such a lowering of the beach would mean even heavier attack of the remaining un-walled section of the beach/road edge. A couple of weekends back I found Days Bay residents gallantly planting more Pingau in the hope they could arrest this possible sea action before it begins.

An interesting observation on which I can only speculate is the line of sand exposed currently by the excavation required to replace the wooden retaining wall. Does that represent an old beach height? Or is it simply the height of old wind blown sand on top of the up-lifted swamp land? The top of an old dune? Whatever the answer it does suggest that there is considerable ongoing beach erosion in this area. Erosion that is likely to be exacerbated by the new hard walls being created.

In Eastbourne, where the houses were falling into the sea in the 1950s, a massive concrete seawall was built on top of sheet steel piling. That essentially failed with the sea rapidly undermining the new concrete wall, leaving it hanging on the sheet piling. Groins, stretching out into the sea, were then placed and maintained for the next 30 years to assist the rebuilding of the sandy foreshore. The photo of that seawall and groins, below, was taken in May 1987.

Then the results of further earthquake action combined with river flooding and the old man in the sea began to deliver tonnes and tonnes of shingle from the Orongorongo river valley, south west around the coast from Eastbourne.

This is quite an extraordinary and on-going event. In 1981 the then Eastbourne Borough Council was very concerned at the possibility of loosing the road in front of the Bus Barns. The sea had taken out much of the foreshore and was within a couple of metres of the tar seal on the road - at the edge of the grass in the photo below. While the council deliberated on what to do and luckily made no hasty decisions to build yet another seawall, the first pebbles of the huge shingle bank that is now there, arrived – and saved the road. The shingle bank is now three time the size of what shows in the photo:

The apparently inexorable movement of the shingle bank then took it around Point Arthur to begin depositing shingle in front of the concrete seawall. In time, as it moved northwards, the groins were removed and the shingle bank grew. People managing the sports ground adjacent to the northern end of the seawall wanted to take advantage of the newly deposited land. There were proposals, plans, discussions, meetings and arguments. Luckily sense prevailed then (although who knows what will happen in ten or twenty years time when the history repositories have departed this bit of the land or this world) and the new beach has been left to expand or contract as natures forces would have it. The photo below was taken from approximately the same position as the earlier photo showing the groins. This one was taken Oct 08.

But now a new problem is presenting itself. This great moving mass of shingle is reaching into Days Bay where it can be seen as ‘destroying’ the good sandy beach. What is to be done? We so often see a problem and think, solution? I do it too. I have just seen the first house I built nearly 35 years ago nearly destroyed by a slip – a slip that I should have foreseen if I hadn’t so much wanted to build there. . .

We could try regular grading of the beach to gather up the shingle to be deposited some other place. We could build a great big break water from Windy point out into the harbour to catch the shingle slug. At least slow it down. That would leave it to build up a huge shingly beach in old Eastbourne for a few years. We could then move the sand dunes westward at Bishop park and widen the park. Or we could mine the shingle as it reaches the north end of the Eastbourne beach or build a mining platform out in the little bay between Eastbourne and Days Bay. I guess if we take the mining or beach grading idea we could be mining for a very very long time. We could mine it. Grind it to sand and replenish the northern end of Days bay beach with it. But where we put the mining plant and crushing machine is a tricky question to answer? NIMFY

Part of the trouble, of course, is that we don’t really know where that shingle might move to or how much more there is to come. Perhaps we do need to recycle it back to Eastbourne south, continually, to protect that end of the Borough.

No! Let us stop, try very hard not to get too emotionally tangled up in seeking a solution for the next 10 to 20 years. Maybe we have to accept nature’s way on this occasion. The hills uplift, erode, uplift, erode. The sea worries away at the shore giving some, taking some back.

Let us watch and marvel.

Tuesday, September 30, 2008

Nude bathing on Eastbourne Beach - NO WAY!

There has been considerable publicity given to Kapiti District Council's move to allow nude bathing along the whole of their coast line. Wellington City Council points out that although there has been a local beach regularly used by nude bathers for some years, they do not have any bylaw against such behaviour and haven't for some time.

I enjoyed finding this reference then in an old Evening Post (7 Jan 1908) that records the passing of Eastbourne's new bylaw prohibiting such practices. And note, they even had swimming code inspectors - caretakers of the PUBLIC GOOD!

Sunday, September 28, 2008

Beech forest damage, Days Bay

Our ecosystems develop in association with the their surroundings (by definition). If one part of the system is disrupted then there may be further disruption in the rest of the system. If a large old tree falls down within a forest there can be many consequences.

Additional light may be let in. Wind can get in. The eventually decaying trunk will provide organic material for soil rejuvenation and so on. When several trees fall with very wet feet, inadequate root systems etc the consequences may be greater. When even more trees are felled by the addition of very strong wind the ecological issues escalate.

There is no doubt that the removal of the pines above Sunshine Bay contributed to the die-back and wind assisted toppling of many Beech trees over the southerly ridge from the Pine Forest and in to Days Bay. To imply that the death of the Beech trees was an almost direct result of the trees being cut from 2006 is simply not good ecological reasoning.

With the Pine Forest over the ridge (shown above) gone, other trees that had grown in it's shelter were now more exposed to the elements. Immediately after the first 'wet feet' and 'wind-blow' fall of pine trees in 2004, trees all around took a beating. First, of course, it was the neighbouring pine trees to those that had fallen - to natures hand, not man's.

The same storms had afflicted the Wellington City pine forest on the Tinakori hills (also 2004) and forced the WCC to lead the way in removing the remainder of their pine forest.

HCC council began cutting in 2005 and as already noted earlier a small stand of Beech on the edge of the northern Days Bay ridge were the first taller trees to die back. Other beech trees that had not grown in the lee of the forest, remained strong and unaffected. Medium height native specimens that had also begun to grow on that northern ridge in the lee of the pine forest also were burnt off.

In the photo above and the one below, of the northern ridge of Days Bay, it is clear that Beech trees can and have, survived strong salt laden winds. These photos were taken September 2008.

The photo below is also interesting in showing the very localised nature of the Beech tree wind-burn when viewed against the surrounding forest cover.

The area of the fallen Beech trees, only 2 years later, is covered with hundreds of Beech seedling many well over a metre high. If the trees were going to suffer die-back from wind burn maybe the good thing that happened was that they were not merely burnt but toppled.

It looks a mess now from afar but close up it a an amazing seedling bed. The uprooted trees effectively loosened soil, provided protection from the sun and moisture retention in the area immediately behind the root balls. There is probably going to be much faster return to a stronger forest than existed before, than if regrowth was happening following a fire.

Beech seedlings growing very strongly (despite a very dry summer) two years after their parents toppled. Look forward to a stronger, more healthy Beech forest.

My next post will consider a little of what we know of this area going back about 150 years. The Bays were cleared, burnt (on purpose and by accident) and farmed. Roads were cut into the hillside, sections were cleared and houses built.

Saturday, September 27, 2008

Pine forest removal, Sunshine Bay - Post #4

This is the fourth instalment on the Sunshine Bay Pine Forest removal, 2004 - 2006. My subsequent instalments on this Pine Forest saga are going to review earlier hazards that these hillsides have been subjected to and that have contributed to the changing shape and cover of the land - clearing, fire & grazing. The Pine Forest was finally cleared during December 2006. Photos show: - loggers working to tie back trunks prior to cutting
- the 'pathway' of a get-a-way log
- the get-a-way log
- the completed result, including the long-term- tie back with wire ropes of many of the fallen trunks (too difficult to remove with a helicopter).

The clean up included the cutting into firewood lengths, one large log that had slipped downhill out of control, just missing the new house being built below.

The logging team were working on a wet Sunday to complete the job, tying back all trunks with large ropes in an endeavour to prevent the log possibly careering sown hill. Despite their efforts one did get a way with the 50 mm rope unravelling itself from its tie-up point. It slid just past the house under construction at the top of Mahina Road.

The photo below, taken in January 2007, shows the hillside after the last of the trees was felled. Clearing up the boundary track still has to be undertaken. One can see the wire ropes placed to secure the trunks from slipping down hill. (All images can be seen in a slightly enlarged format by clicking on them.)

Further photos indicate how well the native tree undergrowth is already coming away strongly in the wetter, more southerly facing slopes and gullies. The photo immediately below is in the area of the top of the gully north of Slip 3" (HCC consultants - Samcon Report dated Oct 2006). The 2nd photo is immediately above 'Slip 3'.There are many hundreds of Rangiora (flowering in the photo below), Whiteywood and a variety of coprosma among many other species. The 2nd photo also shows some of the seedlings planted by an HCC work team who did an excellent job, digging deep holes such that many of the seedling. survived the dry summer of 2007. In the last couple of months further replanting has taken place. There has also been a further slip that unfortunately took out several seedlings and now also threatens the path across the top of the slips. That pathway was originally put in along with the pine seedlings in the 1930's. It was taken out in many places during the slips over the last 4 years with the author undertaking re-alignment work in an effort to keep the access open - valuable in the case of fire apart from recreational, restoration and maintenance work.

On the drier, westerly and northerly slopes one can expect a lot more gorse re-growth. However, where an uprooted pine tree provides some shelter native cover is likely to sprout and flourish. natural growth has also been supplemented with specific plantings. There is, unfortunately, also a lot of Boneseed. An earlier HCC report did suggest that they would be removing the Boneseed weed during their Maintenance programmes. Although they have done well removing pine seedlings it appears as though they have decided to fore-go the removal of Boneseed.
It was from this area that the small 'lahar' arose (mentioned in a much earlier post).

The next post will discuss the 'burning' of a large patch of Beech forest over the ridge to the south, in Days Bay.