Wave runup
Definition of Wave runup:
Wave runup is the maximum onshore elevation reached by waves, relative to the shoreline position in the absence of waves.
This is the common definition for Wave runup, other definitions can be discussed in the article

Notes
Wave runup is the sum of wave setup and swash uprush (see Swash zone dynamics) and must be added to the water level reached as a result of tides and wind setup (Fig. 1). Wave runup on a beach is generally due to socalled swash bores: the uprush of waves after final collapse on the beach. Wave runup is an important parameter for assessing the safety of sea dikes or coastal settlements.
By waves is meant: waves generated by wind (locally or on the ocean) or waves generated by incidental disturbances of the sea surface such as tsunamis, seiches or ship waves. Wave runup is often indicated with the symbol [math] R [/math].
For waves collapsing on the beach, a first orderofmagnitude estimate is given by the empirical formula of Hunt (1959) ^{[1]}^{[2]}^{[3]},
[math]R \sim \eta_u + H \xi , [/math]
where [math]\eta_u \sim 0.2 H[/math] is the wave setup, [math]H[/math] is the offshore significant wave height and [math]\xi[/math] is the surf similarity parameter,
[math]\xi = \Large\frac{ m}{\sqrt{H/L}}\normalsize = T \, m \, \Large\sqrt{\frac{g}{2\pi H}}\normalsize , \qquad (2)[/math]
where [math]L = g T^2/(2 \pi)[/math] is the offshore wave length, [math]m = \tan \beta[/math] is the beach slope and [math]T[/math] is the peak wave period. The horizontal wave incursion is approximately given by [math] R / m[/math].
Many other empirical formulas have been proposed for the runup. A popular formula for the runup [math] R_2[/math] exceeded by only 2 % of the waves for given [math]H, L[/math] has been developed by Stockdon et al. (2006^{[4]}), based on a large dataset:
[math] R_2 = 1.1 \; (\eta_u + 0.5 \sqrt{S_w^2 + S_{ig}^2} \, ) , \qquad \xi \ge 0.3 , \qquad R_2= 0.043 \; \sqrt{HL} , \qquad \xi \lt 0.3 , \qquad (3) [/math]
where [math]\eta_u = 0.35 H \xi[/math] is the wave setup, [math]S_w=0.75 H \xi[/math] is the swash uprush related to incident waves and [math]S_{ig}=0.06 \sqrt{HL}[/math] is the additional uprush related to infragravity waves. The factor 1.1 takes into account the nonGaussian distribution of runup events.
From an inventory of runup formulas by Gomes da Silva et al. (2020^{[5]}), it appears that for steep beaches ([math] m \gt 0.1[/math]) the runup increases with increasing beach slope (approximately linear dependance^{[6]}), while for gently sloping dissipative beaches ([math] m \lt 0.1[/math]) the dependence on beach slope is weak or absent^{[6]}^{[4]}. In these latter cases, runup is dominated by infragravity waves, that yield a small runup that increases with increasing wave height (approximately linear dependence^{[7]}^{[8]}). Field observations^{[9]} and numerical models^{[10]} also point to a dependence of infragravity swash on the frequency spread and the directional spread of incident waves. The largest infragravity swash has been observed for incident waves with a small directional spread and a large frequency spread.
In cases where the backshore berm or foredune of dissipative sandy beaches is artificially protected with gravel or cobbles, the runup [math] R_2[/math] exceeded by only 2 % of the waves when the water level during storms reaches higher than the toe of the cobble berm revetment, can be estimated from the approximate empirical formula^{[11]}
[math] R_2 \approx 4.14 \, h_{toe} m_{berm} +0.66 , \qquad (4) [/math]
where [math]h_{toe}[/math] is the water depth at the toe of the berm and [math]m_{berm}[/math] is the berm slope.
The accuracy (rootmeansquare deviation) of runup predictions using empirical formulas such as (1), (3) or (4) is usually not better than [math]0.25 \, R[/math].^{[3]} The general applicability of empirical formulas for runup prediction based on simple parametric representations of beach and shoreface is limited due to the influence of the more detailed characteristics of the local beach and shoreface bathymetry (e.g., beach permeability and groundwater level, curvature of the beach profile, crescentic bars, or swash acceleration along the horn of a beach cusp embayment^{[12]}). The tide level may influence the wave runup due to wave breaking on nearshore sandbars.^{[13]} The applicability of empirical formulas for the wave setup, which is a substantial component of the runup, is limited for similar reasons. Accurate estimates of the wave runup require insitu observations or detailed numerical models.
Related articles
References
 ↑ Hunt, I.A. 1959. Design of seawalls and breakwaters. J. Waterw. Harbors Division ASCE 85: 123–152
 ↑ Holman, R.A. and Sallenger, A.H. 1985. Setup and swash on a natural beach. J. Geophys. Res. 90: 945–953
 ↑ ^{3.0} ^{3.1} Atkinson, A.L., Power, H.E., Moura, T., Hammond, T., Callaghan, D.P. and Baldock, T.E. 2017. Assessment of runup predictions by empirical models on nontruncated beaches on the southeast Australian coast. Coast. Eng. 119: 15–31
 ↑ ^{4.0} ^{4.1} Stockdon, H.F., Holman, R.A., Howd, P.A. and Sallenger, A.H. 2006. Empirical parameterization of setup, swash, and runup. Coast. Eng. 53: 573–588
 ↑ Gomes da Silva, P., Coco, G., Garnier, R. and Klein, A.H.F. 2020. On the prediction of runup, setup and swash on beaches. EarthScience Reviews 204, 103148
 ↑ ^{6.0} ^{6.1} Nielsen, P. and Hanslow, D.J. 1991. Wave runup distributions on natural beaches. J. Coast. Res. 7: 1139–1152
 ↑ Ruessink, B.G., Kleinhans, M.G. and Van Den Beukel, P.G.L. 1998. Observations of swash under highly dissipative conditions. J. Geophys. Res. 103: 3111–3118
 ↑ Ruggiero, P., Holman, R. A. and Beach, R. A. 2004. Wave runup on a highenergy dissipative beach. J. Geophys. Res. 109, C06025, doi:10.1029/2003JC002160
 ↑ Matsuba, Y. and Shimozono, T. 2021. Analysis of the contributing factors to infragravity swash based on longterm observations. Coastal Engineering 169, 103957
 ↑ Guza, R.T. and Feddersen, F. 2012. Effect of wave frequency and directional spread on shoreline runup. Geophys. Res. Lett. 39: 1–5
 ↑ Blenkinsopp, C.E., Bayle, P.M., Martins, K., Foss, O.W., Almeida, L.P., Kaminsky, G.M., Schimmels, S. and Matsumoto, H. 2022. Wave runup on composite beaches and dynamic cobble berm revetments. Coastal Engineering 176, 104148
 ↑ Kim, L.N., Brodie, K.L., Cohn, N.T., Giddings, S.N. and Merrifield, M. 2023. Observations of beach change and runup, and the performance of empirical runup parameterizations during large storm events. Coastal Engineering 184, 104357
 ↑ Guedes, R.M.C., Bryan, K.R., Coco, G. and Holman, R.A. 2011. The effects of tides on swash statistics on an intermediate beach. J. Geophys. Res. 116, C04008