Laboratory experiments were conducted to understand how a tsunami-like solitary wave runup can be reduced in one horizontal dimension against the effects of the slope and forest width in cross-shore direction. The wave height to depth ratio from 0.1 to 0.4 was used. The resultant transmitted wave height and maximum runup for the plane slopes of 1/4 and 1/7 were measured and compared with the forest on the same slopes. The dimensional analysis was used to pick up important parameters for comparing the maximum runup effect. The runup can be reduced to 28% by increasing forest width in cross-shore direction. The damping factor for the wave runup without the forest model can be increased from the range of 22% to 75% up to the range of 31% to 98% with the introduction of forest width for non-breaking waves. Thus, a forest on gentle beach slope helps to increase more resilience against tsunami attack even when energy reduction at the beach slope is not sufficient enough.