47 * Currents and Morphological Changes in the Surf Zone on a Sandy Beach Yoshiaki KURIYAMA, Littoral Drift Division, Port and Airport Research Institute 1 1 1) ρd M M x y 2 + + = (1) t x y 2.1 M x UM UM x y + + = t x y η U U ρgd + LD + LD (2) x x x y y 1 2 S S xx xy + + τ bx x y (1) (2) (2)x y ρ D = h + η h * 239-826 3-1-1 E-mail: kuriyama@pari.go.jp η t M x = ρdum y = ρdv UV x y L
48 S xx S xy radiation stressτ bx xy x y radiation stress 2,3) 2.2 2 9) 3 2 6-8) 2.3.5.7 3 3 2 4) X 3.1 V P P 5)
49 Berm Inner bar 6 4 7 5 4 8 5 6 inner bar inner bar 1m2m tombolo salient 78 3.2 D.L.+1.4m 2m 8cm (m)
5 4.1 196 197 9 1m/s 2m/s 14 13m 1.58 16 13) 1 2.1 1 9 2m m 1m 24 47.84 2.1m 1m 12 1 1.5m 13.6m/s 1m 3m 4
51 3m 4.2 2cm 2.2 1m 2 1m 12 3m 18,19) Hazaki Oceanographycal Research Station, HORS 11 4m 8) (3) U FLOAT U 8) (3) U =. 81U FLOAT (3) 1987 199 4 HORS 11 13 y bar y peak 14 85 Renier 2) 12
52 13y bar y peak 15 14 y peak -y bar 5cm/s 21) (2)C d ρ a W 2 sinα w C d 15 ρ a W α w.5 C d.1.1 4.4 4.3
53 1 N P115m 5 4.2 1987 P19m 21 15 HORS P285m -5 16-1 S P38m 87 88 89 9 91 92 93 94 95 96 97 98 99 1 Time(year) 16 115m P115m 1 N P2m Case 1 5 5 P2m P2m P3m P3m Case 2-5 17 R n 18 R /( ) n = U sn U s1 + U s2 + U s3 (4) Case 3-5 R n n U sn n P115m P19m S P285m P38m -1 87 88 89 9 91 92 93 94 95 96 97 98 99 1 Time (year) 17 19 P115m 1 Case 3 8 6 18 4 2 Case 1 Case 2 18 P24m 17 1 2 3 4 Seaward Distance (m) P2m 18 Alongshore Distance(km) Alongshore Distance (km) Contribution Rate (%)
54 5 6 Case 1 4 2 6 Case 2 4 2 6 Case 3 4 2 1) -3-2 -1 1 2 3 199814. Breaking Wave Direction (degree) 2) 19 1973161-163. 3) 24 19815-53. 19 HORS 4) Longuet-Higgins, M. S.: Longshore current generated by obliquely incident sea waves, 2, J. Geophys. Res., 75-33 (197) 679-681. P2m 5) Galvin, C. J. and Eagleson, P. E.: Experimental study of longshore currents on a planar beach, P2m Tech. Mem. U.S. Army Coast. Eng. Res. Cent., 1 P3m (1965) 1-8. 6) Thornton, E. B. and Guza, R. T.: Surf zone longshore currents and random waves: field data and models, J. Physical Oceanography, 16 (1986) P2m 1165-1178. P3m 7) 37 (199) 21-214 8) 26 39 (1992) 196-2 9) 31 (1984) 123-127. 1) 27,28 26-2 (1987) 63-96. 11) 36 Frequency
55 (1989) 354-358. 12) T.C.: Longshore currents over barred beach, Proc. Coastal Dynamics 95, (1995) 413-424. 21-2 21) (1982) 53-16 13) Kuriyama, Y.: Investigation on cross-shore 635 (1999) 97-111 sediment transport rates and flow parameters in 22) the surf zone using field data, Rep. Port and Harbour Research Institute, Vol.31, No.2, pp.3-58, 43 (1996) 356-36 1991. 23) 14) 1973179-183. 15) Sonu,C.J.: Field observation of nearshore circulation and meandering currents, J. Geophys. Res., 77-18 (1972) 3232-3247. 2) Reniers, A.J.H.M., Thornton, E.B. and Lippmann, 43 (1996) 366-37 24) 5 (23) 391-395 16) 25) 21 51 (24) 146-15 (1974) 347-354. 26) 17) 163 (1973) 95 51 (24) 136-14 27) 18) 4 (1993) 266-27 43 (1996) 546-55 19) Kuriyama, Y.: Hydro- and morpho-dynamics on a 28) barred beach, Technical Note of the Port and Airport Research Institute, 128 (22) 6. 44 (1997) 661-665