From: Revegetation of steeplands in France and New Zealand: geomorphic and policy responses
Attribute/Action | East Coast New Zealand | Southern Prealps France |
---|---|---|
Terrain | Moderately steep | Low elevation mountains |
Geology | Cretaceous and Tertiary rocks, mudstones, sandstones, argillites | Jurassic and Cretaceous sedimentary rocks, marls |
Climate | Rainfall 1000 – 2500 mm | Mountainous with Mediterranean influences |
Susceptible to cyclones | Mean annual rainfall 850–1000 mm | |
Convective storms in headwaters | ||
Historical deforestation - when | Some pre-1800’s most late 1800’s and early 1900’s | Neolithic period |
15th and 19th centuries human-induced erosion | ||
Historical deforestation - why | Some vegetation clearance by Maori pre-1850 | Climate change and agriculture expansion |
Widespread vegetation clearance by early Europeans 1880’s | Industrial demand for wood | |
Recognition of “problem” | Early warnings 1920’s | Early 19th century |
Big floods 1938-1947 | Late 19th century hillslope erosion, head water channels aggrading | |
Policy intervention | Soil Conservation and Rivers Control Act 1941 | Reforestation in mountains 1860 – Restauration des terrains en Montagne Act (RTM) |
Catchment Board 1944 | Other laws to control erosion 1864, 1882 | |
Demise of New Zealand Forest Service 1987 | Erosion control programme lasted 50 years up to First World War | |
East Coast Forestry Project 1993 | ||
Revegetation | New Zealand Forest Service plantings 1960’s | Species used - Pinus ngira J.F.Arnold |
Species used - Pinus radiata | Protection forests 120 - 140 year old trees | |
Protection/production forests | ||
30 year old trees before harvesting | ||
Landscape response | Observations of hillslope processes slowing 1980’s - 1990’s | Decrease in sediment yield |
Headwater channel responses 1990’s | River incision | |
Main channel responses not observed but constant | Reduced flows in some rivers | |
Channel interventions | Raising stop banks | Dams |
Gravel extraction |