A simplified analytical method to predict the height of waves transmitted through permeable structures has been developed by making use of small amplitude long waves progressing in permeable media. In the theoretical development conservations of mass and of the mean energy are maintained, and of pressure intensity are assumed at a junction dividing two different media. The transmission coefficient which is the ratio of the transmitted wave height to the incident wave height, is given as a function of incident wave characteristics, and the width, porosity and permeability of the structures. The coefficient decreases for structures of greater width and of smaller permeability, and for waves of greater height and of smaller period, and at smaller depth. Comparison between the theory and the experiments of idealized rubble structures shows that there are close agreements for the structures of relatively greater size of rocks and of thinner width.