Activity Group: Flood Protection and Control Works Activity: Flood Protection and Control Works Wairau Floodplain Tributaries How this Activity Contributes to the Vision and Related To keep key Wairau River tributary (including the Wairau above the Waihopai confluence) channels as clear of trees and debris as is economically practical, to Community Outcomes maintain flood capacity and to minimise the risk of changes to channel alignment. This Activity helps to achieve the Vision by protecting both high-value enterprises and Sounds Watercourses Flood Management the wider community from flood damage. It contributes to the Community Outcomes of Environment, People, Economy, Connectivity and Living as outlined below. To develop and maintain a river capacity and standard of protection for flood sizes of Outcomes Actions up to a one in 50 year return period for the Waitohi and the Waikawa (and their tributaries) flowing through the urban areas of Picton and Waikawa. Similarly, to Environment Providing flood control and drainage services has major consider waterway improvements in other built up Sounds areas including Havelock in People environmental, economic and social benefits because: order to protect houses. Economy - residents and their properties are safeguarded from the Connectivity risks of river and stream flooding and erosion Blenheim, Riverlands and Renwick Stormwater Outfalls - agricultural drainage of the lower Wairau plains improves To ensure the system of drains, natural watercourses, pumping stations and Living the productivity of drainage impaired soils. floodgates adequately provides for the disposal of urban stormwater from the pipe Managing soil conservation at the Wither Hills Farm Park prevents networks operated by Council’s Assets & Services Department. The desired level of sediment from depositing into the watercourses at the base of the service is to provide for a one in 50 year return period event. hills. Lower Wairau Floodplain Drainage Managing gravel extraction from river channels in a sustainable manner avoids environmental impacts and provides a valuable To provide agricultural drainage for the Wairau floodplain land, generally to the east of economic resource. Blenheim and O’Dwyers Road. This involves controlling weed and sediment for 280 km of excavated drains or natural watercourses, maintaining floodgated culverts into Providing for secondary uses on Council owned floodway land the major rivers, and providing pumping stations (generally with a capacity of removing enables public access and recreation, ecological/amenity 15 mm of rainfall in 24 hours). The riparian margins of selected channels are managed plantings and economic gain through forestry or pastoral leasing in an aesthetic and ecologically sensitive manner. as appropriate. What is this Activity About? Gravel Extraction To manage gravel extraction from river channels throughout Marlborough to ensure The Activity is primarily about managing flood hazard and drainage, and occurs in the that the extraction of this valuable economic resource is managed in a sustainable more developed areas of Marlborough. Requirements in different areas have manner consistent with good river management. This requires limiting gravel extraction developed according to the history of flood risks and development of drainage to specific amounts and locations. improvements, or from more recent assessment of flood risks as land uses have changed and development occurred. The objectives for this activity are outlined below. Gibson’s Creek Rewatering Lower Wairau Flood Protection To supply water from the Wairau and Waihopai rivers into Gibson’s Creek to meet the requirements of the Southern Valleys Irrigation Scheme and to provide further water to To maintain and upgrade the main Wairau floodplain floodways below the Waihopai ensure a continuous flow in the Gibson’s Creek/Opawa system to meet environmental confluence to provide a capacity for flood sizes up to a one in 100 year return period. objectives, including groundwater recharge. These floodways include the Wairau (below Waihopai), the Wairau Diversion, and tributaries including the Opawa, Taylor and Omaka Rivers and the Riverlands Co-op Soil Conservation Floodway. To manage the Wither Hills Farm Park so that little or no sediment is deposited into the watercourses at the base of the hills. 2018-2028 Long Term Plan Page 74