2.3.4 Natural Environment Marlborough can be separated into two distinct areas, each with its own climate, topography and vegetation types. The Marlborough Sounds north of the Wairau River receive up to 2,500mm of rainfall per annum which can fall in heavy bursts causing rapidly rising river levels in the steep catchments that make up the area. The Te Hoiere/Pelorus catchment has a history of severe flooding and continues to overtop its banks on a regular basis. Much of the land has been farmed at some stage but most of the hill slopes are now covered in manuka dominated scrub, native beech/podocarp forest or production pine forest. The broader valley floors of the Rai, Te Hoiere/Pelorus and Linkwater are predominantly converted to dairy farms. The Department of Conservation manages large areas of the Marlborough Sounds including the majority of the foreshore reserves and the Kokomohu Marine Reserve in the Queen Charlotte Sound/Tōtaranui. Most islands in the Sounds are also managed by the Department and many have been successfully eradicated of mammalian pests. Maud and Takapourewa (Stephen’s) Islands are of international significance to conservation and d’Urville Island is important as a possum free habitat. Awatere Valley The Wairau River experiences the typical, dryer east coast climate and rainfall drops off to an average of only 750mm per annum. Drought is a common theme and Blenheim is regularly the sunniest township in New Zealand. Apart from the braided Wairau and Awatere River plains the majority of the land is rolling hills running into steeper country as altitude increases. Many of the upper catchments have permanent snow through the winter months and Mt Tapuaenuku in the upper Awatere is the highest mountain outside of the Southern Alps. The predominant vegetation types are tussock grasslands and grey scrub with an enormous amount of biological endemism which has adapted to the harsh dry colder areas of inland Marlborough. 2.3.5 Human Modification Although much of the Marlborough Sounds was farmed up until the 1960s, most of them have reverted back to native scrub and forest or been planted in pinus radiata. Transportation costs (barging) meant sheep and cattle farming became uneconomic however at the same time the sheltered waters of the Sounds were identified as ideal for aquaculture and since that time 575 green-lipped mussel farms have been established, mostly in the Pelorus Sound/Te Hoiere. Salmon farms have also been established in Marlborough Civil Defence Emergency Management Plan, 2017-2022 Page 25