1. Hightown Dune Restoration Scheme and the River Alt Update – September 2013 Graham Lymbery Sefton Council

2. Hightown Dune Restoration Scheme Payments Main ContractorRevetment 352,332.71 Sand Dunes 865,086.43 1,217,419.14 other works 67,798.86 environmental site management plan 9,434.00 fees 232,832.77 310,065.63 total 1,527,484.77 Balances as at 31st March 2013 £ for Environmental works 90,521.28 for maintenance 28,261.51

3. Hightown Dune Restoration Scheme

4. Beach -4,568m 3 Dunes -5,490m 3 Beach -1,788m 3 Dunes -16,108m 3 2006 - 2008 Loss to System -27,954m 3

5. Hightown Dune Restoration Scheme Beach +933m 3 Dunes +3,094m 3 Beach +353m 3 Dunes +9,439m 3 2008 – 2010 2008/09 Loss 2009/10 Gain Gain to System +13,819m 3

6. Hightown Dune Restoration Scheme Beach +6,649m 3 Dunes -55m 3 Beach +3,503m 3 Dunes +13,489m 3 where placed and 3,209m 3 blown into dunes 2010 – 2013 28,000 added as part of scheme Gain to System +26,850m 3

7. Historic changes to the tidal Alt channel Maps show the river having a east to west alignment in the 1600s By the 18 th century, its alignment was shown as roughly north-south (Blott et al., 2006) with its mouth around a kilometre further north than at present Continued accretion from the north gradually forced the river southwards During the last century the channel has attempted to establish a balance against a background of wider human intervention, including the construction of navigation training walls and extensive dredging activity.

8. Changes to the tidal Alt channel since 1945 Relatively stable planform Significant change to ‘Hightown’ bend between the northern outfall and rubble spit meander development followed by cut- through after 1980 Progressive landward movement of the channel since 1945 to hug Alt training wall 2005 channel along the Hightown section is at its most easterly position recorded since 1945 1945-51 1951-61 1961-65 1965-74 1974-78 1978-80 1980-82 1982-85 1985-93 1993-97 1997-2002 2002-08 2008-13 All

9. Changes to the tidal Alt channel since 1945 Relatively stable planform Significant change to ‘Hightown’ bend between the northern outfall and rubble spit meander development followed by cut- through after 1980 Progressive landward movement of the channel since 1945 to hug Alt training wall 2005 channel along the Hightown section is at its most easterly position recorded since 1945

10. Meander development River Bollin, Cheshire (Hooke, 2004) A natural process which occurs when a river crosses unconsolidated (soft) floodplain material Meanders begin to form when flows are not uniform across the river (eg. as a result of obstacle) Distinct inner and outer bends encourage further bend development (positive feedback) with outer bend erosion and inner bend deposition The bends tighten until a cut off forms (see Hightown in 1980) and the sequence begins once again Several theories proposed, but key variables include bank strength, flow speeds, sediment availability. Hightown situation is complicated further by the impact of waves and tidal currents

11. Recent changes and pressures Physical modifications Accretion of Taylor’s Bank including longshore sediment transport from the north Flood and Coastal Risk Management – dune recharge Meander bend development (black line shows approx channel position in 1980) Oblique photo taken in 2012 (c) North West England and North Wales Coastal Group

12. The role of physical ‘hard points’ Hard points will influence meander development – United Utilities northern outfall – Sailing club sea wall – ‘Rubble’ spit Altcar Rifle Range Hightown Village Blundellsands Sailing Club UU Outfall Dune recharge SC landing stage West Lancs Golf Club Tidal Alt Channel Altmouth PS Formby Bank Rubble spit

13. Altmouth Pumping Station Built in 1972 and refurbished with new electric pumps in 2011. Modified regime = – No difference at higher tidal stages – The amount of water flowing across the tidal Alt was, and continues to be a factor of tidal range and catchment rainfall. – release of river water is more gradual than before so that ‘low water’ levels are sustained at a higher level, for longer, than before. These flows not considered to be significant in terms of geomorphic change. – No difference during storm conditions.

14. The future The channel has moved before and will continue to do so Outer bend erosion and inner bend accretion will continue to drive meander bend development Uncertain where main meander loops will form History and presence of hard points and potentially more resistant substrate point to bend developing on seaward side. The growth of Taylor’s bank from the west may affect this trend. Enhanced monitoring and annual reporting of results is recommended, particularly between the rubble spit and the UU outfall.