THE ROCKS ROAD SLIPS

Nelson Evening Mail, 3 August 1916, Page 5

THE ROCKS ROAD SLIPS

REPORT BY COUNTY ENGINEER

The following report on the recent slips on the Rocks Road was presented to the YVai-mea 'County. Council to-day by the County Engineer JMr G. S>. Whiteside) i

One result of the recent flood was a large slip of 300 to SCO tons on the County portion of the Tahuna-Port road. This caused traffic to be suspended until a track could be excavated through it. To hasten this operation, portion of the debris was thrown over the sea wall, ■while the carts were being tipped. It is in this connection that the absurd: interpretation of Section 209 of the Harbours Act appears when applied to this road. Tjhig Section seeks to prohibit the deposit into the harbour of anything, so as to be, or tends to the injury of navigation. The area of the land' drained into the Nelson Haven, by the Maitai river, Brook and other streams is appi-oximate-ly 120,000 acres. The rainfall producing the flood was recorded as 4 inches, or 400 tons of water to the acre. Tests from the Maitai river showed there was about 1 pea- cent, of earthi silt in solution being carried down by the. storm water. This works' out as 480,000 tons eroded and washed 1 down from slips and land slides. This quantity is not unusual in other parts. Count it as 200,000 tons, most of which would be precipitated into the inner harbour, some probably being carried through the cut in the Bouldler Bank, and l some through the ' old channel at Arrow Rock toward Tahuna. If this 200,000 tons of silt, brought into the harbour by storm water does not in/jure navigation, it is absurd to suppose that the 2000 tons' of slips on the Rocks Road would' be worth oensidering, even though it didl drift- into the Port or fairway. But from' careful observations of local conditions -made during the last five years, T am in a position to show that the earth tin-own from the Rocks Road, when in solution, drifts toward Tahuna. The earth's strong diurnal current and the tidal flow sets in from the east by 'Cook's Strait, through the French Pass. This mighty ocean stream l strikes' the land at -Maekav.'s Bluff, and has thus formed the Boulder Bank Spit. The large stones propelled by this powerful current here finds a lodgment.' The' smaller particles worn off the moving stones 'by attrition and the action of the water, is carried by the sea current, augmented -bv the Maitai river,. drifts westward and forms the Sands and' the Tahuna flats. It is. therefore, safe to assert from the evidence that scarcely a particle of spoil from the Bocks road would -interfere with navigation. And it would therefore be no breach of Section 209 to cast earth slips over the sea wall. • ' lOr. Macmahon said the Harbour-master held that sand' was brought towards the-: harbour during storms, and the Marine .Department had absolutely prohibited - spoil being put over the wall. The suggestion that a wall. be erected' further. out seemed a good l one.

Cr. Best said the.bulk, of the stuff was taken the other way, not into the, harbour. Debris went down the Maitai in thousands of tons and filled up the harbour, yet nothing was said I .about, that.,; Or. Corder moved, and it was carried, that the Chairman and Cr; Best_ interview the City Council with a view to a'bating the; trouble on the; Rocksv road, the two engineers to also attend the con-,; ference.