Summary
Prior to that in 2004 we completed the Brighton Marina to Ovingdean coast protection scheme, 1.8km of seawall encasement, reconstruction of the Undercliff Walk, groyne encasement and cliff stabilization and protection works, 2 years to complete.
The South Downs SMP stated that for the study area Brighton Marina to Ovingdean it is necessary to “Hold the Line” (i.e. to maintain the coastal defences on the current line), in order to protect the infrastructure and the existing urban development.
Prior to 2003 the existing defences were close to the end of their life but were not allowed to ‘fail’, as repairs had been undertaken when necessary to sustain the seawall. However if the coastal defence was to be maintained the seawall needed strengthening and the promenade and splash wall was in need of replacing.
The options for this defence length were:
- Continue current maintenance, then Do Nothing at most economic time which is year 3.
- Continue current maintenance. Replace defences at most economic time which is year 4
- Replace existing defences in year 1 with Pre-cast encasement of wall with concrete apron and removal of some groynes.
- Replace existing defences in year 1 with Pre-cast encasement of wall, rock fillet toe over the wall length, encasement of the groynes over the beach lengths, remainder of groynes left in situ.
- Replace existing defences in year 1 with Pre-cast encasement of wall, rock revetment over the wall length, encasement of the groynes over the beach lengths, remainder of groynes left in situ.
- Replace existing defences in year 1 with Pre-cast encasement of wall and new offshore breakwaters.
- Replace existing defences in year 1 with Pre-cast encasement of wall and new groynes over whole length.
Chosen option
Option 4 – Replace existing defences in Year 1 with Precast encasement of wall with rock fillet over the wall lengths and encasement of the groynes over the beach lengths.
Present value cost over 50 years £ 7.93 million
Present value benefits over 50 years £24.71 million
Benefit/cost ratio 3.11
