As beach vulnerability to erosion and associated coastal flooding increases with rising sea levels and more intense coastal storms, our understanding of storm waves and the resulting wave runup (e.g., waves generated by large North Pacific storms, hurricanes, tropical Storm Sandy) is still limited. My thesis fieldwork obtained quantitative observations of the wave runup and changing sand levels in response to large ocean waves. Existing field observations of wave transformation from offshore to wave runup in large conditions are very sparse, reflecting the difficulty of working in this harsh environment. These observations were used to calibrate and improve a numerical model (SWASH) to evaluate its fitness for coastal planning and beach management in extreme conditions when shoreline infrastructure is most at risk.