Discussion on Papers 12–14

MR REYNOLDS, Paper 13

The approach to the design and construction of

outfall, must begin with the determination of

the environment, i.e. the forces of Nature, and

the soil conditions on the route or alternative

routes. Without that an economic design and method cannot be evolved. An economic design is

one which is secure, but not excessively secure,

against the forces of Nature, and one which can

be installed without excessive or incalculable

installation risks.

The parameters in paragraph 8 of the Paper may be illustrated by reference to two studies which involve wave predictions using the methods referred to in paragraph 11. In one, which is off the Yorkshire coast, the 100 year return period offshore wave is 9 m significant. At 1 km from the coast, where the water depth is 18. m, such a wave would produce a transverse current on a sea bed pipe of 2.6 m/s. Combined with a tidal current of