A one-dimensional numerical model of the Thames, used with a com- 

 plete range of surges added to the tide, gives maximum amplitudes of 

 surge occurring before high tide and of the order 25 percent larger than 

 without tide. The maximum outer levels occur close to high tide. 



A "parallel" numerical model, with tide and surge calculated 

 separately but interactions occurring between them, gives an indication 

 that quadratic friction terms are more important to the interaction than 

 the nonlinear advective terms, u3u/9x. 



Coastal Engineering Significance. This paper shows from field data 

 that there is a definite interaction between storm surge and tides, such 

 that the surge in an estuary can be significantly amplified by tidal 

 currents . 



The detailed modeling of the interaction terms is of wider 

 interest. In particular, the importance of the friction term should be 

 considered in other types of wave-current interaction. 



49. SCHUMANN, E.H., "Changes in Energy of Surface Gravity Waves in the 

 Agulhas Current," Deep-Sea Research, Oxford, England, Vol. 23, No. 

 6, June 1976, pp. 509-518. 



Keywords. Comparison of Theory and Measurement; Current Refraction; 

 Currents, Nonuniform; Currents, Ocean; Observation; Wave Energy; Wave 

 Observation; Waves, Ocean; Waves, Wind. 



Discussion. After a brief discussion of the theory, details of the 

 method of measuring wave spectra, wind, and current are given. The 

 spectra are frequency spectra measured by a shipborne wave recorder, 

 but visual estimates of wave direction are also given. The character of 

 the sea state, both in and outside the Agulhas Current, is determined 

 using data from 15 pairs of stations, occupied daily over a 7-day 

 period. 



The energy density, E, at the station with weakest current was 

 extrapolated to zero current, Eq, by assuming a linear variation and 

 comparing with other "weak current" measurements. E/E^ could then be 

 evaluated at a station in a strong current (1.1 to 1.6 meters per 

 second) . 



A comparison is made with results from LONGUET-HIGGINS and STEWART 

 (1961, 1964) for waves propagating onto a directly adverse current, for 

 the two cases where the current variation is due to vertical and to 

 horizontal inflow. The experimental points show quite reasonable 

 agreement considering the uncertainties involved. 



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