Saturday, March 05, 2005
A tsunami propgation model on the Web?
This service could be the start of something really useful: as well as the public notification via Civil Defence, the Web-based notification could be to an email address, accessible from your own cell phone. The more such services get out there, the more robust the model becomes. There is always the caveat: as seagulls well know, stuff happens locally. The gust which gives Brother Gull Jonathon a quick case of the runs, out over the dunes, passes unnoticed by Sister Gull Theresa who happens to be rootling through the rubbish bins by the Pier. Tsunami are very localised beasts, just like hail-storms. As they say in that really big country north-north-east of here, 'your mileage may vary'.
Tuesday, March 01, 2005
New Brighton Revitalisation – revisited.
It’s been repeated so often it has become a cliché - the one about Christchurch being the only city in the world where the rich live by the airport and the slums are along the beach. Every so often there is a newspaper article about the bright new feature of the beach suburbs, but we are still waiting. And the slums are certainly there: turn south at Beresford Street and glance right.
Three years ago after a major public meeting, The New Brighton Revitalisation Committee was formed – a combined effort of CCC and locals.
They started well, produced some very pretty brochures and came up with a plan, though they seem to have forgotten that they promised to report back to the local community on a regular basis.
The essential vision statement for the 'revitalisation' project is here.
As vision statements designed by a committee go, this is not too bad. Note the emphasis on ‘encourage investment… commercial and new residential’. Now think of the progress made on this point, three years on. There’s been a lot of land change hands. But visible construction? None.
All we have got is some physical infrastructure improvements (connecting beach to mall via narrowing of Marine Parade, for example, even if the kerbing is positively Albanian in both design and execution).
Can a Council or a Committee make any realistic progress on ‘encouraging investment’? Of course they can. By getting out of the way of those with a commercial interest, and letting them get on with residential development. All else then follows.
The NB revitalisation plan tries to anticipate e.g. the type of retail outlets a revitalised mall would contain. But these things grow organically, and a biological model is more to the point: businesses always follow the consumer dollar.
The first and most obvious ‘development’ needed is residential beach apartment towers. These would house a stable core of local customers, who together with the wider retail catchment, and those attracted by events and other local activities and amenities, would become customers for an increasing range of local businesses.
Get the people into apartments first, and then stand back and watch the cafes, bookshops, hairdressers, galleries, arthouse cinemas (the old Joyland theatre is currently up for sale…), set up and chase those dollars.
That isn’t to suggest that the community abandon design guidelines and other restrictions or requirements for these new residential constructions. Far from it: we need some new ones, of which more later.
But for heaven’s sake, let the dog see the rabbit first. Stop trying to micro-manage revitalization, and let the private sector do what it does best: provide us with things we want and are prepared to pay for.
What could slow or stop development?
There are three aspects which have the potential to seriously restrict the natural flow of investment needed for the developments which constitute the true revitalization.
One is the Coastal Plan Review.
The second is the City-wide review of possible District Scheme changes.
The third is the fear generated by recent “expert” pronouncements about tsunami.
These come in two flavours: Distant, and Near.
These are all discussed, then tied together by some Civil Defence and planning suggestions that offer a way forward.
Three years ago after a major public meeting, The New Brighton Revitalisation Committee was formed – a combined effort of CCC and locals.
They started well, produced some very pretty brochures and came up with a plan, though they seem to have forgotten that they promised to report back to the local community on a regular basis.
The essential vision statement for the 'revitalisation' project is here.
As vision statements designed by a committee go, this is not too bad. Note the emphasis on ‘encourage investment… commercial and new residential’. Now think of the progress made on this point, three years on. There’s been a lot of land change hands. But visible construction? None.
All we have got is some physical infrastructure improvements (connecting beach to mall via narrowing of Marine Parade, for example, even if the kerbing is positively Albanian in both design and execution).
Can a Council or a Committee make any realistic progress on ‘encouraging investment’? Of course they can. By getting out of the way of those with a commercial interest, and letting them get on with residential development. All else then follows.
The NB revitalisation plan tries to anticipate e.g. the type of retail outlets a revitalised mall would contain. But these things grow organically, and a biological model is more to the point: businesses always follow the consumer dollar.
The first and most obvious ‘development’ needed is residential beach apartment towers. These would house a stable core of local customers, who together with the wider retail catchment, and those attracted by events and other local activities and amenities, would become customers for an increasing range of local businesses.
Get the people into apartments first, and then stand back and watch the cafes, bookshops, hairdressers, galleries, arthouse cinemas (the old Joyland theatre is currently up for sale…), set up and chase those dollars.
That isn’t to suggest that the community abandon design guidelines and other restrictions or requirements for these new residential constructions. Far from it: we need some new ones, of which more later.
But for heaven’s sake, let the dog see the rabbit first. Stop trying to micro-manage revitalization, and let the private sector do what it does best: provide us with things we want and are prepared to pay for.
What could slow or stop development?
There are three aspects which have the potential to seriously restrict the natural flow of investment needed for the developments which constitute the true revitalization.
One is the Coastal Plan Review.
The second is the City-wide review of possible District Scheme changes.
The third is the fear generated by recent “expert” pronouncements about tsunami.
These come in two flavours: Distant, and Near.
These are all discussed, then tied together by some Civil Defence and planning suggestions that offer a way forward.
Coastal Plan Review
Present Coastal plan priorities give first place to ‘conservation’. This is frankly dopey, since there is endless argument over what is being conserved. It certainly is not the original beach, with its low or absent, ever-shifting dunes. It currently seems to be the ‘conservation’ of man-made dunes, created with the non-native sand binders of Marram and Ice-plant which now form the most prominent vegetation. Except, of course, where there aren’t any dunes – North Beach surf club, and Central Brighton. There, presumably, we are conserving stone seawalls and paved carparks.
Proponents of keeping the Coastal policy exactly as is (i.e. Conservation focused) need to acknowledge that this policy acts directly against the revitalization process. By trapping the beach and dunes in a 1980’s time-warp as to uses, dune contour, width and height, they are standing in the way of revitalization.
This ‘conservation’ objective needs to be replaced by a zoned approach which emphasizes particular priorities for distinct zones. After all, the beach from the Waimakariri Mouth to the tip of the Southshore spit is just too diverse for a one-size-fits-all Coastal policy.
It seems more intelligent to zone off the beach priorities just as the land uses on the shore side are themselves zoned. Five distinct zones can be identified by a glance at what lies behind the dunes now.
1. From Waimairi Surf Club to Thomson Park should be recreation and amenity focused
2. Central NB area down to Shackleton Street should definitely be commercial/residential Recreation amenity focused in keeping with the Revitalisation intention
3. Between Shackleton Street (which marks the beginning of the old 5-chain wide Beach Reserve) and Tern Street, some combination of ‘wild experience’ with a mild conservation-cum-recreation focus would seem appropriate.
4. South of Tern Street, the dunes are privately owned,
5. The Spit area itself is a Conservation area with a focus on migratory birds.
These changes would provide something for everyone and avoid the locked-in, one policy for all approach which is currently in place. If you wanted a latte in a tiki bar by the beach, you could go to Central NB or North Beach. If you wanted to bird-watch you could go to the tip of the Spit. If you wanted to drive your 4WD on the beach you could get a permit at Spencer Park and go up the Waimak Mouth spit. If you wanted a ‘wild’ experience but close to the city, you could get on your bike and go somewhere between Shackleton and Tern streets. If you want to find a decent size wave you could try the artificial reef. Beach-sail or kite-surf could be for hire just south of the Pier. And you could still walk the doggies almost anywhere but the marked areas, s’il vous plait.
Differential zoning would make it much more workable than the present tunnel-vision policy emphasis. So the policy suggestion is:
Review the Coastal Plan policies with a view to zoning, allowing differing priorities in different zones, and to harmonise these with the Revitalization Plan.
Proponents of keeping the Coastal policy exactly as is (i.e. Conservation focused) need to acknowledge that this policy acts directly against the revitalization process. By trapping the beach and dunes in a 1980’s time-warp as to uses, dune contour, width and height, they are standing in the way of revitalization.
This ‘conservation’ objective needs to be replaced by a zoned approach which emphasizes particular priorities for distinct zones. After all, the beach from the Waimakariri Mouth to the tip of the Southshore spit is just too diverse for a one-size-fits-all Coastal policy.
It seems more intelligent to zone off the beach priorities just as the land uses on the shore side are themselves zoned. Five distinct zones can be identified by a glance at what lies behind the dunes now.
1. From Waimairi Surf Club to Thomson Park should be recreation and amenity focused
2. Central NB area down to Shackleton Street should definitely be commercial/residential Recreation amenity focused in keeping with the Revitalisation intention
3. Between Shackleton Street (which marks the beginning of the old 5-chain wide Beach Reserve) and Tern Street, some combination of ‘wild experience’ with a mild conservation-cum-recreation focus would seem appropriate.
4. South of Tern Street, the dunes are privately owned,
5. The Spit area itself is a Conservation area with a focus on migratory birds.
These changes would provide something for everyone and avoid the locked-in, one policy for all approach which is currently in place. If you wanted a latte in a tiki bar by the beach, you could go to Central NB or North Beach. If you wanted to bird-watch you could go to the tip of the Spit. If you wanted to drive your 4WD on the beach you could get a permit at Spencer Park and go up the Waimak Mouth spit. If you wanted a ‘wild’ experience but close to the city, you could get on your bike and go somewhere between Shackleton and Tern streets. If you want to find a decent size wave you could try the artificial reef. Beach-sail or kite-surf could be for hire just south of the Pier. And you could still walk the doggies almost anywhere but the marked areas, s’il vous plait.
Differential zoning would make it much more workable than the present tunnel-vision policy emphasis. So the policy suggestion is:
Review the Coastal Plan policies with a view to zoning, allowing differing priorities in different zones, and to harmonise these with the Revitalization Plan.
City-wide review of possible District Scheme changes
The council is about to look at District Scheme and prioritize areas that need to be to be reviewed. If Brighton doesn’t come to the top of the list this could mean further delays in potential development. And the review would need to be consistent with the intentions of NB revitalization goal of ‘encouraging development’.
What do developers need by way of ‘encouragement’? In a word: certainty. This comes in three dimensions.
1. Certainty of a sale of their developed residential units, homes, apartments etc. And this comes down to one factor: sea views. Without a single cent of Council promotion, as shown by the high prices paid for rundown properties, developers can already smell the salt laden air of our beach. But why would you invest in an apartment by the sea, with a stunning view of the back end of a sand dune? The policy answer to this question is equally simple:
height restrictions could be stated as a guaranteed number of storeys with a clear sea view.
This would give a developer certainty that ‘x’ floors times ‘y’ units per floor could be sold, and would avoid the eternal question of just how high those dunes in front actually need to be.
2. Certainty as to process. As the recent Ferrymead debacle has demonstrated, developers need to be confident that a plan submitted in good faith, conforming to current District Plan requirements, is not going to be side-swiped by a public which distrusts the approval process itself. Developers in NB will be committed to several million dollars in land acquisition before the plans are submitted, so any significant increase on their holding time to completion can mean financial disaster. Imagine the extra interest on $3m, if an unanticipated appeal drags the planning process out by a couple of years. The policy answer is simply to ensure that there is proper communication between Councils, developers and their publics, and (less simply!) that the public broadly speaking can live with any proposal conforming to current District Plans. For instance, the revitalization plan notes that ‘Residential development on the beachfront limited to 5 – 7 story apartment style buildings’ would be appropriate. With the proviso that Certainty #1 can be met (the ‘clear sea views’ principle), this does seem like a good start.
3. Certainty about design guidelines. This is a notoriously subjective and hard-to-get-right area: Sydney’s ‘Toastrack’ by Circular Quay happened despite planning guidelines and despite a proximity to the justly famed Opera House, and the architecturally acclaimed Sumner beach front apartments have not met with much public enthusiasm. It’s quite easy to nominate some of the jam-packed, tiny, apartment developments in central Auckland as examples to be avoided. But it’s much harder to provide positive guidelines. There is definitely one area where new design guidelines are needed, and that is Tsunami refuge provision – see below for a fuller explanation. Briefly, it means using a robust form of construction, and keeping the first couple of storeys relatively clear so that a tsunami wave could just flow straight through them. As the two lower storeys in these developments will likely have Glorious Dune Views anyway, devoting them to mundane uses such as car parking and amenities such as gymnasia or pools, is not much of a disincentive for developers.
These ‘encouragements’ are what the Council should be considering for the proposed changes to the District Plan for NB.
However, it doesn’t get us off to a good start when ECan Regional Councillors talk at local meetings about stopping some of the planned aspects, such as the artificial reef, or when the revitalization plan itself tries a bit of social engineering (‘Residential developments should cater for all age and income groups’).
Many locals surf, and an artificial reef has a great potential for generating more consistent waves. This would in turn feed into commercial surfing ventures, further visitors, and more events. There has to be serious, substantive arguments to accompany any ECan objection to an artificial reef: we haven’t heard any yet.
As for accessibility of beach front residential units to low-income people: let’s be frank: that train left the station at around the time waterfront sections hit the $300,000 mark. Was this guideline applied to Sumner? Does it apply to Fendalton? Is the Council prepared to observe its own design guidelines for the beachfront developments, and to put our rates money where its mouth is to acquire land and do the development? This aspect of the plan needs to be just quietly ignored.
What do developers need by way of ‘encouragement’? In a word: certainty. This comes in three dimensions.
1. Certainty of a sale of their developed residential units, homes, apartments etc. And this comes down to one factor: sea views. Without a single cent of Council promotion, as shown by the high prices paid for rundown properties, developers can already smell the salt laden air of our beach. But why would you invest in an apartment by the sea, with a stunning view of the back end of a sand dune? The policy answer to this question is equally simple:
height restrictions could be stated as a guaranteed number of storeys with a clear sea view.
This would give a developer certainty that ‘x’ floors times ‘y’ units per floor could be sold, and would avoid the eternal question of just how high those dunes in front actually need to be.
2. Certainty as to process. As the recent Ferrymead debacle has demonstrated, developers need to be confident that a plan submitted in good faith, conforming to current District Plan requirements, is not going to be side-swiped by a public which distrusts the approval process itself. Developers in NB will be committed to several million dollars in land acquisition before the plans are submitted, so any significant increase on their holding time to completion can mean financial disaster. Imagine the extra interest on $3m, if an unanticipated appeal drags the planning process out by a couple of years. The policy answer is simply to ensure that there is proper communication between Councils, developers and their publics, and (less simply!) that the public broadly speaking can live with any proposal conforming to current District Plans. For instance, the revitalization plan notes that ‘Residential development on the beachfront limited to 5 – 7 story apartment style buildings’ would be appropriate. With the proviso that Certainty #1 can be met (the ‘clear sea views’ principle), this does seem like a good start.
3. Certainty about design guidelines. This is a notoriously subjective and hard-to-get-right area: Sydney’s ‘Toastrack’ by Circular Quay happened despite planning guidelines and despite a proximity to the justly famed Opera House, and the architecturally acclaimed Sumner beach front apartments have not met with much public enthusiasm. It’s quite easy to nominate some of the jam-packed, tiny, apartment developments in central Auckland as examples to be avoided. But it’s much harder to provide positive guidelines. There is definitely one area where new design guidelines are needed, and that is Tsunami refuge provision – see below for a fuller explanation. Briefly, it means using a robust form of construction, and keeping the first couple of storeys relatively clear so that a tsunami wave could just flow straight through them. As the two lower storeys in these developments will likely have Glorious Dune Views anyway, devoting them to mundane uses such as car parking and amenities such as gymnasia or pools, is not much of a disincentive for developers.
These ‘encouragements’ are what the Council should be considering for the proposed changes to the District Plan for NB.
However, it doesn’t get us off to a good start when ECan Regional Councillors talk at local meetings about stopping some of the planned aspects, such as the artificial reef, or when the revitalization plan itself tries a bit of social engineering (‘Residential developments should cater for all age and income groups’).
Many locals surf, and an artificial reef has a great potential for generating more consistent waves. This would in turn feed into commercial surfing ventures, further visitors, and more events. There has to be serious, substantive arguments to accompany any ECan objection to an artificial reef: we haven’t heard any yet.
As for accessibility of beach front residential units to low-income people: let’s be frank: that train left the station at around the time waterfront sections hit the $300,000 mark. Was this guideline applied to Sumner? Does it apply to Fendalton? Is the Council prepared to observe its own design guidelines for the beachfront developments, and to put our rates money where its mouth is to acquire land and do the development? This aspect of the plan needs to be just quietly ignored.
Tsunami and Brighton.
There has been a good deal of public fear-mongering in articles since the Dec 26th Indian Ocean earthquake. While the possibility of a tsunami is ever-present, what we need to do in the here-and-now is actually quite simple.
In a Distant Tsunami alert, follow the Civil Defence instructions in the back of the Yellow Pages.
In a Near Tsunami situation, there is no plan yet and no available refuges. Don your life jackets.
Let’s examine these two very different situations more closely.
First of all, tsunami can originate either from a Distant or a Near source. Their effects are quite different.
Distant Tsunami
We know quite a lot about Distant tsunami and their historical effects, and there is a Pacific Ocean tsunami warning system in place, thanks to US efforts after the 1960 tsunami which had disastrous effects in Hawaii.
Distant tsunami arrive after an earthquake along an American (South or North) fault line. They take at least 12 hours to cross the Pacific, and thus there is plenty of time to organize and carry out the existing Civil Defence plan. This advises a retreat from the coast of several kilometers, or a climb to at least 35 metres above sea level.
The historical pattern of distant tsunami effects on our immediate coastlines is also quite predictable. Tsunami are affected by two factors: the sea-bed profiles offshore, and the coastline shape itself. Anything offshore (such as reefs – artificial or natural, islands), can act to dissipate energy. Other features such as submarine canyons can act to focus it. Both effects have been observed in Canterbury.
Generally speaking, the broad beaches of Pegasus Bay have seen only minor wave run-ups from Distant tsunami. These have been contained by existing seawalls (e.g. by North Beach Surf Club and at Central Brighton), by dunes elsewhere, or else the waves have simply been too small to be noticeable – their energy was directed elsewhere.
However, in any confined area – the Waimak mouth, the Estuary, Sumner, and all of the Peninsula bays plus Lyttelton Harbour, the tsunami waves tend to be focused and intensified. Houses were carried away at Okains and Le Bons Bay in the 1868 tsunami, and 3-5 metre waves are consistently recorded for Lyttelton during most significant tsunami.
The NOAA website and tsunami search engine here has a useful summary of historical tsunami effects locally. Search for coordinates -43 North to -46 South, and from 172 West to 179 East, and run-up country “New Zealand” to pick up the East Coast around Canterbury.
But as noted, there is at least time to prepare for such an event. We cannot realistically save buildings in the bays, but we can save ourselves. And as was the case for the recent North Island floods, these events are insurable, so that the loss of buildings and houses is not necessarily an economic problem. There is time to collect personal objects of value.
In short, a Distant Tsunami is not something to be feared. Prepared for, insured for, planned for, trained for - yes. On notification, the drill is – follow the Civil Defence instructions in the back of the Yellow Pages. And don’t rush – there is time, and you need to be sensible.
In a Distant Tsunami alert, follow the Civil Defence instructions in the back of the Yellow Pages.
In a Near Tsunami situation, there is no plan yet and no available refuges. Don your life jackets.
Let’s examine these two very different situations more closely.
First of all, tsunami can originate either from a Distant or a Near source. Their effects are quite different.
Distant Tsunami
We know quite a lot about Distant tsunami and their historical effects, and there is a Pacific Ocean tsunami warning system in place, thanks to US efforts after the 1960 tsunami which had disastrous effects in Hawaii.
Distant tsunami arrive after an earthquake along an American (South or North) fault line. They take at least 12 hours to cross the Pacific, and thus there is plenty of time to organize and carry out the existing Civil Defence plan. This advises a retreat from the coast of several kilometers, or a climb to at least 35 metres above sea level.
The historical pattern of distant tsunami effects on our immediate coastlines is also quite predictable. Tsunami are affected by two factors: the sea-bed profiles offshore, and the coastline shape itself. Anything offshore (such as reefs – artificial or natural, islands), can act to dissipate energy. Other features such as submarine canyons can act to focus it. Both effects have been observed in Canterbury.
Generally speaking, the broad beaches of Pegasus Bay have seen only minor wave run-ups from Distant tsunami. These have been contained by existing seawalls (e.g. by North Beach Surf Club and at Central Brighton), by dunes elsewhere, or else the waves have simply been too small to be noticeable – their energy was directed elsewhere.
However, in any confined area – the Waimak mouth, the Estuary, Sumner, and all of the Peninsula bays plus Lyttelton Harbour, the tsunami waves tend to be focused and intensified. Houses were carried away at Okains and Le Bons Bay in the 1868 tsunami, and 3-5 metre waves are consistently recorded for Lyttelton during most significant tsunami.
The NOAA website and tsunami search engine here has a useful summary of historical tsunami effects locally. Search for coordinates -43 North to -46 South, and from 172 West to 179 East, and run-up country “New Zealand” to pick up the East Coast around Canterbury.
But as noted, there is at least time to prepare for such an event. We cannot realistically save buildings in the bays, but we can save ourselves. And as was the case for the recent North Island floods, these events are insurable, so that the loss of buildings and houses is not necessarily an economic problem. There is time to collect personal objects of value.
In short, a Distant Tsunami is not something to be feared. Prepared for, insured for, planned for, trained for - yes. On notification, the drill is – follow the Civil Defence instructions in the back of the Yellow Pages. And don’t rush – there is time, and you need to be sensible.
A Near Tsunami
But what about a Near Tsunami – one caused by (say) an earthquake in the offshore faults under Pegasus Bay?
The first point is there has not been one in our recorded history, so we know very little about possible effects. But three good assumptions can be made from other Near Tsunami, such as the one which hit New Guinea in 1998. Firstly, it will be relatively soon after the quake – minutes, not hours. Secondly, it will be high enough to overtop any reasonable seawall, dune or other coastal defence. Thirdly, it will be energetic enough to go a fair distance inland. In the 1998 New Guinea quake, for example, a 10+ metre high wave washed a village on a spit into the lagoon beyond, crossed the lagoon, and carried on for 1.3 km into the coastal mangrove forest beyond. Details are at NOAA
A good place to start is to model the effects of a Near Tsunami: New Scientist (Issue 2482 P 16) notes that the Pacific Marine Environmental Lab in Seattle has software which has accurately replicated the Boxing Day tsunami in the Indian Ocean. Policy suggestion is straightforward:
Fund the modeling of a Near Tsunami caused by a Pegasus Bay fault rupture
There is absolutely no way to plan a conventional Civil Defence evacuation for a Near Tsunami. The wave run time is just too short – minutes, probably. And it cannot be assumed that any Avon bridges would actually remain usable. There is concern over all the Avon bridges’ ability to withstand a large, local earthquake - the working assumption has to be that these bridges are unusable.
And as Guy Fawkes night regularly demonstrates to us all, even if those bridges are open, getting out of Brighton fast enough to outrun a Near Tsunami is really not a viable option.
This means that we have to look to our immediate environment for help – within the distance we could run in say 10 minutes.
In Japan, which sits on the junction of three highly active tectonic plates, some coastal cities maintain a series of what are termed ‘tsunami towers’ to which locals can escape. As ‘New Scientist’ (Issue 2482 p 13) notes, these are reinforced structures, and locals are trained to ‘run for the tower’ immediately a large local quake is detected.
So, if we had a tower to run to, our best bet is to ‘run for the tower’.
The first point is there has not been one in our recorded history, so we know very little about possible effects. But three good assumptions can be made from other Near Tsunami, such as the one which hit New Guinea in 1998. Firstly, it will be relatively soon after the quake – minutes, not hours. Secondly, it will be high enough to overtop any reasonable seawall, dune or other coastal defence. Thirdly, it will be energetic enough to go a fair distance inland. In the 1998 New Guinea quake, for example, a 10+ metre high wave washed a village on a spit into the lagoon beyond, crossed the lagoon, and carried on for 1.3 km into the coastal mangrove forest beyond. Details are at NOAA
A good place to start is to model the effects of a Near Tsunami: New Scientist (Issue 2482 P 16) notes that the Pacific Marine Environmental Lab in Seattle has software which has accurately replicated the Boxing Day tsunami in the Indian Ocean. Policy suggestion is straightforward:
Fund the modeling of a Near Tsunami caused by a Pegasus Bay fault rupture
There is absolutely no way to plan a conventional Civil Defence evacuation for a Near Tsunami. The wave run time is just too short – minutes, probably. And it cannot be assumed that any Avon bridges would actually remain usable. There is concern over all the Avon bridges’ ability to withstand a large, local earthquake - the working assumption has to be that these bridges are unusable.
And as Guy Fawkes night regularly demonstrates to us all, even if those bridges are open, getting out of Brighton fast enough to outrun a Near Tsunami is really not a viable option.
This means that we have to look to our immediate environment for help – within the distance we could run in say 10 minutes.
In Japan, which sits on the junction of three highly active tectonic plates, some coastal cities maintain a series of what are termed ‘tsunami towers’ to which locals can escape. As ‘New Scientist’ (Issue 2482 p 13) notes, these are reinforced structures, and locals are trained to ‘run for the tower’ immediately a large local quake is detected.
So, if we had a tower to run to, our best bet is to ‘run for the tower’.
How does all of this discussion tie in with Brighton revitalization?
As you have probably noticed, none of the Pegasus Bay beach suburbs has any structures approaching a useful ‘tsunami refuge’ height (probably at least 20 metres).
And as part of the revitalization (arguably the first, most important step) high-density residential apartment development is seen as part of the vision.
The buildings themselves are likely to be apartment towers, built as standard commercial structures, using load-bearing columns to support large floor plates. This is a very robust, well understood construction technique, and has a couple of great advantages for Near Tsunami protection.
Firstly, provided the lower storeys are designed with either no walls or walls which will ‘pop out’ under wave pressure, the structure can act just like a bridge. The supporting columns present little area for the waves to attack, and the water flows harmlessly through the first and possibly second storeys.
Secondly, if sufficient clear floor space on plates above the expected tsunami level is available for public refuge, those spaces become the escape route and refuge for a significant number of local residents. Such floor space can accommodate a surprising number of people: if you’ve ever looked at an elevator’s certificate of fitness and wondered how they can get all those people in, well, in a tsunami you could pack a refuge space to that sort of density.
Developers have to provide a ‘reserve contribution’ as part of the development’s contribution to open public reserve space. The suggestion here is quite straightforward:
i) require developers of multi-storey towers to provide accessible refuge space for x people above a designated height, in lieu of or as part of the Reserve Contribution.
ii) Require pop-out walls up to a designated tsunami height, and design the building itself in conformance to tsunami robustness standards.
The refuge space does not add to development costs, as that contribution has to happen anyway whether in cash or provision. It does require that physical space be set aside – but this could be as simple as an extra-wide stairwell. In any case, such details are for the engineers and planners to sort through: we are concerned here just with the broad principles.
So to summarise what citizens can be told in Civil Defence advice, once these refuges are available:
in a Near Tsunami, run to the nearest designated Refuge Tower and climb as high as possible.
In a Distant Tsunami alert, follow the Civil Defence instructions in the back of the Yellow Pages.
And as part of the revitalization (arguably the first, most important step) high-density residential apartment development is seen as part of the vision.
The buildings themselves are likely to be apartment towers, built as standard commercial structures, using load-bearing columns to support large floor plates. This is a very robust, well understood construction technique, and has a couple of great advantages for Near Tsunami protection.
Firstly, provided the lower storeys are designed with either no walls or walls which will ‘pop out’ under wave pressure, the structure can act just like a bridge. The supporting columns present little area for the waves to attack, and the water flows harmlessly through the first and possibly second storeys.
Secondly, if sufficient clear floor space on plates above the expected tsunami level is available for public refuge, those spaces become the escape route and refuge for a significant number of local residents. Such floor space can accommodate a surprising number of people: if you’ve ever looked at an elevator’s certificate of fitness and wondered how they can get all those people in, well, in a tsunami you could pack a refuge space to that sort of density.
Developers have to provide a ‘reserve contribution’ as part of the development’s contribution to open public reserve space. The suggestion here is quite straightforward:
i) require developers of multi-storey towers to provide accessible refuge space for x people above a designated height, in lieu of or as part of the Reserve Contribution.
ii) Require pop-out walls up to a designated tsunami height, and design the building itself in conformance to tsunami robustness standards.
The refuge space does not add to development costs, as that contribution has to happen anyway whether in cash or provision. It does require that physical space be set aside – but this could be as simple as an extra-wide stairwell. In any case, such details are for the engineers and planners to sort through: we are concerned here just with the broad principles.
So to summarise what citizens can be told in Civil Defence advice, once these refuges are available:
in a Near Tsunami, run to the nearest designated Refuge Tower and climb as high as possible.
In a Distant Tsunami alert, follow the Civil Defence instructions in the back of the Yellow Pages.
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