Error in flood work estimates

Press, 1 September 1980, Page 11

Error in flood work estimates

A. special tribunal set up by the North Canterbury Catchment Board found an 11.4 per cent error in calculations prepared by the Christchurch Drainage Board for flood protection and drainage work on the Lower .Styx River. This could have meant that the figures calculated for stop-banks and flood levels were too low. A report from the tribunal •has been. presented to a •meeting of the North -Canterbury Catchment Board’s water committee. It recommended that three applications from the Christchurch Drainage Board for /water rights for work on. the "Lower Styx River be rejected. The tribunal considered applications to dam parts of the river by building stop--hanks to prevent flooding, to Increase flows from the Rhodes Main Drain, and to .increase the discharge of the .board’s pumping station and build a-by-pass for floodwaters.

' The tribunal came to its decision after hearing submissions from the applicant and objectors, evidence from ryo special witnesses, and after visiting the site. It upheld the objections of Mr L A. Louwinger, Mr- J. H. Brown, Mr and Mrs K. P. Bond, Mr C. H. G. Curragh, who is the president of the Brooklands Community Centre, and Mr F. J. Knoef.

In examining the evidence, the tribunal noted an error in the Christchurch Drainage Board calculations. The error was 11.4 per cent in the design flow, which meant that calculations for bank heights, freeboard, and flood levels would be too low.

In an additional report, the tribunal said that a complete appreciation of al! parties had been lacking in the preparation of all the Styx River schemes. The drainage and flooding problems faced by residents and farmers in the Brooklands, Kainga Road and Spencerville areas had to be considered.

The cost of damage done to the community and ways to avoid the damage should also be investigated. “In making this statement the tribunal is not unmindful

of the continuing efforts made at great expense by the Christchurch Drainage Board over the last 12 years to solve the Styx problem, but it is pointed out that the downstream-problem has to be resolved before any progress can be made upstream,” the report said.

Further economic and technical investigations also had to be made.

In conclusion, the report said that the board would proceed with construction of the new Styx floodgates as soon as economic conditions permitted. The next stage was to investigate a Lower Styx drainage and river control scheme that would satisfy all parties. "No scheme is ever likely to receive general accepts ahce unless it first solves

the real problems of drainage and flooding to the urban lands of the Lower Styx,” it said. Only then could the job of protecting upstream farming land be accomplished, with more water being discharged through the floodgates and out to sea.

Members of the tribunal were Messrs M. J. O. Dixon, E.- B. Palmer and P. Sheehan. The chairman of the board (Dr W. R. Holmes), said the report included a series of statements that were critical of another local authority. “If, in fact, the remarks that are made in the docu-

ment are true, I am surprised that some of the points mentioned were not picked up by our staff when they reviewed the last report,” he said. “I would not like to come out being publically critical if it was said we were as much to' blame as the Drainage Board.” Mr Dixon said the supplementary report was purely for information and was intended for discussion at a later date.

The meeting agreed that the report should be received and that the recommendations be sent to the parties involved in the hearing.