Marlborough Sounds Resource Management Plan Large river catchment and tributaries with a range of river types including: • Steep-gradient, dendritic watercourses in the upper Pelorus; • Deep entrenched meander system in the middle Pelorus; • Floodplain meanders where the river terraces are aggrading in the mid- Rai; and • A low gradient shallow, straight-sided type in the lower Pelorus and Wakamarina. Terraces generally have fertile soils, especially on low terraces and where fresh silts are being deposited. 2. Climate and Elevation Cool temperate to cold, moist to wet climate. Winter frosts typical - severe on valley floors. Temperature inversion and cold air drainage and ponding into valleys very pronounced. Wide annual temperature range. Little or no ameliorating effects from the sea. Droughts uncommon. Very high incidence of valley fog. Warm summer temperatures in sheltered valleys. Relatively high rainfall: 1600-2000+ mm Highest at Pelorus and Wakamarina headwaters. Occasional very intense rainfall events. Frequent flooding of terraces characteristic of the Rai and lower Pelorus catchments. Water ponding in swales is common. Valleys sheltered from strong winds and storms. High ridges and Richmond Range very exposed to prevailing westerly winds and storms. Winter snow on Richmond Range frequent. Other than estuary and delta areas, no maritime or coastal influence. High elevation: 0-1756 m altitude range; mean altitude 480 m. 3. Water Excellent water quality (especially clarity) in Pelorus headwaters. Generally degraded in all lower reaches, (especially from eutrophication) particularly in Rai River, as a result of intensive agriculture. B. The Biological Environment [Part of Pelorus Ecological District] Total land area in Pelorus ecosystem is 66,985 ha of which; 69% is in native forest, 4% is in shrubland (mainly exotic), 12% is in plantation forestry and 15% is in pasture and non-forest native cover. (Note: Percentages based on interpretation of 1990 satellite images.) 1. Predominant Indigenous Vegetation Detailed in Table 10 Originally all forested except for discrete high altitude alpine areas, tidal flats and estuaries, riparian communities with the flood zone of the main rivers, active floodplains and deltas, a few valley non-forest wetlands, some bluff communities and slip sites. App Two - 50