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By Kip Brook
The 800 hectare Bottle Lake Forest 10km north east of central Christchurch should be urgently investigated as a safe option for relocating the quake hit Christchurch eastern suburbs.
The suggestion was made today by Di Lucas, the former president of the New Zealand Institute of Landscape Architects.
The Bottle Lake area is owned by Christchurch City Council and the forest managed by the Selwyn Plantation Board and, excepting for a couple of small sand flat pockets, has not been affected by the earthquakes’ liquefaction.
``Could pines be cleared and houses built on the elevated back-dune lands that avoid sea level rise issues? The suburbs and areas the houses are removed from could then become public reserve land.
``Clearing the pine forest would result in carbon debit payment, but removing the housing from sand flats would enable the restoration of that land into permanent native forest cover, offsetting the pine loss. Such an option ought to be investigated,’’ Lucas said.
Prime Minister John Key has said government had a clear picture of what land would have to be abandoned but is not naming the areas or putting a time frame on when home owners will be told. Lucas also suggested the Rawhiti golf course at New Brighton as another option.
She said the severe liquefaction from Monday’s double shakes appeared in areas already formally identified by the council as flood prone and since February 22 these land areas had dropped. Thus flood proneness has increased there. The sand flats have liquefaction and the dunes don’t. Sadly, much planning and development has ignored the underlying character, she said.
The point has been reinforced in the central city where in quake after quake, regardless of repairs by the council, the routes of the old stream levees have exploded. Even if the underlying stream has for decades been piped away, the levee lands remain and they have reacted.
This is a reminder that the memory of the stream remains in the land. Capping springs and piping away the waters does not prevent certain natural processes from continuing. Levees have exploded, resulting in lateral spread, both where streams still occur on the surface and where they have long been diverted away.
``The need to allow for existing and previous stream patterns is an indication of the need for any recovery plan to be a spatial plan. It must involve lines on maps. The public and property owners deserve more than a high level policy document. They need assurance that resilient development, environmental quality and community friendly dimensions will be adequately addressed in each area.
``So, will the Central City Recovery Plan be any use? While tens of thousands of good ideas have been contributed to council, in my opinion these are worthless if they are not translated into principles and strategies, clearly stating what is and is not wanted, and spelled out for each particular area.
``A plan without lines on maps is a waste of time. The recovery plan must involve spatial planning. A plan that involves just bullet point lists threatens to be mere tokenism whilst people ignore the nice words and carry on as before.
``A Structure Plan, or at least an Outline Development Plan, is essential to provide assurance to land owners and community of what the Council’s plan for the central city is proposing. A wish list is not enough.’’
She also recommended a shift from 100 percent runoff in the CBD toward a zero runoff regime, using permeable paving, rain gardens and vegetated surfaces. This would reduce river flooding and contamination. Down the track, council could buy properties with a water asset, with source springs. Council could collaborate with re-building to provide a green linkage between streets. The corner of Salisbury and Barbadoes Streets is an example of spring flow that was exposed after the Council bought and removed a house.
Lucas has reviewed the 1850s maps of Christchurch showing wetlands and streams through the city. Liquefaction had long ago been predicted, and has occurred on eastern areas with high water table and estuarine sands, and the existing and former natural levees along watercourses have exploded.
These are a reminder that the underlying natural state of land needs to be carefully considered in renewed city layouts. The explosion of old levees (the natural stream banks made of silt), was evident across rural and urban Christchurch from the September, February and June quakes.