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Tiromoana Bush is located in coastal North Canterbury in the Motunau Ecological District (Lowry Ecological Region). This ecological district comprises coastal hills and valleys, all below 600 metres asl, drained mostly to the east by small rivers. The geology is highly varied including greywacke, argillite and Tertiary sedimentary rocks, Quaternary outwash gravels, and coastal gravels and sands. Tiromoana Bush is located within very old (1.8 to 65 million years) former seabed strata on the coastal side of Mt Cass and is consequently underlain by generally fine-grained compacted sedimentary deposits. The valley has moderately steep sides with surface erosion evident. Soils are broadly described as Stoneyhurst Hill soils, dominated by sandy loams.
The coastal environment consists of narrow sand and shingle beaches covered at high tide (Russell & Brown 1990). The beaches are backed by coastal cliffs up to 60 metres high. Slumping has occurred in the cliffs of the lower reaches of Kate Valley and nearby streams.
The annual rainfall of Kate Valley is 921 mm (1986-2000 average), although as with the rest of Canterbury, there is considerable variation both within years and especially between years. The area typically experiences warm dry summers and cool wet winters. Snow is rare, although frost can occur in winter, especially in valley bottoms away from the coast.
Russell, P. & Brown, J. 1990. Coastal Resource Inventory. First Order Survey. Canterbury Conservancy, Department of Conservation, Wellington.