While the Cashmere Valley is a natural ponding zone for upper catchment stormwater runoff prior to discharging to the Cashmere Valley Stream, both historical data and modelling carried out by the Christchurch City Council has allowed for an accurate assessment of flood depths in the area. Important points to note are that Stage 1 development will be raised significantly from the valley floor and sited at an elevation of 19.55 m RL (approximately the same height as Shalamar Drive which has not been subjected to any historical flooding) and this is over 0.5 m higher than the lowest point in Worsleys Road, as a result water would be released from the Valley across the road rather than increasing to such a height as to affect the Stage 1 area. As part of ongoing works within the Valley, upstream detention facilities are to be constructed, these will effectively increase the total storage capacity of the upper valley and result in less flooding occurrences in the lower.
There are several significant benefits to the Stage 1 development. It will not be subject to flooding due to the significant height it will be raised to (a lot higher than many surrounding properties that have not been subject to historical flooding). The lower lying Valley can never be built over and therefore owners have the peace of mind of being able to have a permanent rural outlook. Cashmere Valley Drain is to be naturalised and beautified and the valley floor is to be re-contoured, landscaped and will have a wetland constructed within it. Thereby providing owners will a stunning visual amenity and recreational playground at their back door over summer periods. Currently much of the valley is flat and does not easily drain which results in water ponding for a significant duration after flood events. However, the re-contouring of the valley will allow water to escape (at a controlled rate) far more easily and therefore allowing the Valley to dry out more quickly than is currently experienced.
