ABSTRACT
7.1 Introduction
So far only individual elements and individual modes of failure have been considered. In practice, a coastal defence or hydraulic structure will have more than one failure mechanism and will often be part of a larger scheme that may contain several or many linked components. The entirety of a drain is a good example, as it may contain not only pipe sections but also joints, junctions, inflows, outflows and stilling tanks, to name but a few components. In a similar vein, a flood defence is likely to comprise several different types of construction along its length, as well as flood gates and barriers. In some cases where there is a change in construction the neighbouring structure provides a key element of stability, so that should it fail then its neighbour would be much more likely to fail too. Such an example would be vertical steel sheet piles, topped with a concrete beam or pad, located next to a mass concrete structure. In the event that the mass concrete structure failed (most likely through gradual deterioration and lack of maintenance), the sheet piling would be at greater risk because water could attack from both front and rear, washing out fines from behind the piles and reducing the integrity of the structure as a whole.
