Appendix F - River Control and Drainage Works Programme 5.1.1.5 Subject to detailed hydraulic confirmation, allow stopbanks flanking wide berms to be brought in closer to the river; and in the Jones Road area to construct a new realigned stopbank. 5.1.2 New Works Required • Deliberate strategic gravel and sediment removal upstream of Ferry Bridge. • Stopbank raising Ferry Road to Watsons Road. • Stopbank relocation below Jones Road. • Stopbank upgrading in vicinity of Eckfords Road. • Straighten and extend guide bank at river mouth. 5.2 Wairau Diversion 5.2.1 Design Intentions 5.2.1.1 Enlarge the existing active channel out to the already constructed rock lines by using strategic sediment removal to encourage and supplement natural erosion. 5.2.1.2 Maintain the existing rock lines that delineate the active channel. 5.2.1.3 Keep the berms hydraulically efficient by keeping in grass cover only. 5.2.1.4 Maintain a directly opening mouth by occasional pilot cuts through the bar. 5.2.2 New Works Required • Strategic gravel and sediment removal, especially at the top of the Diversion and downstream of Rarangi Bridge. 5.3 Flow Division Area of Lower Wairau and Diversion Including Road and Rail Bridges (Note: This covers from the road bridge to 1.5 km down each river reach). 5.3.1 Design Intentions 5.3.1.1 To improve the waterway capacity of this reach so as to reduce flood levels in a 5,800 m/sec flood to below road and rail bridge soffit levels.3 This will be done by gravel and other sediment removal. 5.3.1.2 To attain a flow split in floods of 45% lower Wairau, 55% Diversion, but in low flow periods of at least 50% in the lower Wairau. 5.3.1.3 To maintain hydraulically efficient channels by removal of trees and debris from the active river channel. 5.3.1.4 To assess the need and design parameters for a flow control structure here. 5.3.2 New Works Required • Strategic gravel and sediment removal. App F - 3