For this coursework, you are required to estimate the 50 year overtopping rate of a coastal defence structure for a location on the UK coastline. The methodology to carry out this coursework is as follows:
- You each have been given a location on the UK coastline. These locations are given in the Appendix.
- For each location you are required to estimate the 50 year return period wave height just offshore of
your site (i.e. in deep water) based on a JONSWAP analysis. You have already been shown how to
do this, but the details will be shown again in the lecture by Dr Dominic Hames.
- Based on the direction of your 50 year wave height calculated, you will then have to carry out a
refraction, shoaling and breaking analysis to determine the wave conditions at the toe of your coastal
defence structure. The assumptions for these calculations are as follows:
a. The depth of water at the toe of your structure is 3m.
b. Assume the structure is a 1 in 3 sloping revetment protected by rock.
c. The beach slope immediately in front of your structure has a 1 in 10 slope (1 vertical to 10
d. Assume that wave heights are limited to a maximum of 60% of the depth of the water at the
e. Determine the wave period assuming that the wave steepness in deep water is equal to 0.04
where steepness is given by equation 1.
f. Assume that the crest of the structure is 2m above the water level.
- Wave overtopping is to be determined based on Owen’s (1980) equations which are given below.
n = steepness (-)
H = wave height (m)
T = wave period (s)
Owen(s) equations are:
𝑄 = 𝑄∗𝑇𝑔𝐻 equation (2)
𝑄∗ = 𝐴 exp(−𝐵𝑅∗
) equation (3)
Q = overtopping rate (m3
A = 0.01090 (constant)
B = 28.7 (constant)
Rc = freeboard (m) (distance between crest height of structure and still water level)