Report: TR05/50

Author: Dr Douglas Hicks

Abstract

This report summarises the results of a survey carried out in May-June 2005. The survey's purpose is to ascertain the extent of vegetative soil conservation cover in the Mangarama catchment, and measure what reductions have accrued from them. This information is required for a five-year review of soil conservation in the Upper Waipa sub-catchments.

The Mangarama catchment has been selected by Environment Waikato staff because they regard it as typical of the Upper Waipa sub-catchments in its terrain, land use, and soil conservation measures.

It is 59 square kilometres in extent, draining north from the Mokau watershed near Te Kuiti and entering the Mangapu, a slightly larger tributary of the Waipa. The western headwaters are an undulating limestone plateau full of sinkholes and caves, with surface drainage in valley bottoms where streams have cut down to underlying greywacke.

West of the Waipa fault, mudstone is dissected into moderate footslopes descending from the limestone plateau to the catchment's middle reaches which are a broad valley floor infilled by alluvial terraces, floodways and drained swamps. The Mangarama's eastern and southern rims are short steep hill country, formed from alternating beds of mudstone, sandstone and limestone.

All landforms in the catchment are mantled by volcanic ash - patchy on the hills, deep on the plateau and footslopes, re-sorted by water on the terraces and floodways.

The survey brief is to :

• identify how much land needs soil conservation.
• ascertain whether such land has vegetative soil conservation measures. These may be spaced tree plantings in pasture, close afforestation with commercial tree species, or natural vegetation (retained, reverting or planted)
• obtain measurements of any changes in soil erosion or disturbance where vegetative soil conservation measures are present.

Soil Conservation Survey of the Mangarama Catchment [PDF, 109 KB]