Liverton Stream culvert SH2 Western Hutt Road: blockage by stream debris 11-12 July 1972

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Oborn, L.E. 1972 Liverton Stream culvert SH2 Western Hutt Road: blockage by stream debris 11-12 July 1972. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 141 7 p.

Abstract: The most convincing of the various hypotheses advanced, attributes the source of the bulk of the rock material blocking the Liverton Stream culvert beneath the SH2 Western Hutt Road to spoil that was dumped over Liverton Road near its junction with the recently constructed Access Road. Geological evidence cannot distinguish between the material derived from construction, widening and maintenance work on these two roads. The dumped spoil built fans in the valley of Liverton Stream that extended down to and across the motorway. Water flowed in some places through these fans, and in other places both through them and over the top of them. High river flows resulting from the very heavy rains preceding the culvert blockage mobilised much of the material in the stream bed and transported this, and material that slipped in from the valley sides, as a ''lahar'' type of flow down the stream into the culvert. (auth)