Severe flooding in coastal areas can happen when extreme ocean, river, and weather conditions combine. Traditional methods for predicting these compound flooding events have limitations. A new approach using a 3-D Fully Nested Archimedean copula with nonparametric marginals shows better performance in modeling these complex events. This method helps in accurately assessing the risk of flooding caused by heavy rainfall, storm surges, and river discharge. Neglecting to consider all three factors together can lead to underestimating the risk of flooding. The study suggests that analyzing trivariate hydrologic events is crucial for understanding and preparing for the increased risk of flooding over time.