花蓮港舊東堤外面對太平洋，其海底坡度甚陡，在改善前其防波堤亦不高，且常遭到巨大的颱風波浪及季風波浪侵襲，越波情形甚爲嚴重。在擴建工程完成前，此越波主要影響僅爲外港，尚可勉強忍受，而第四期擴港工程完成後，此越波水域即成爲內港水域，且會影響新建碼頭之安全性。
本研究即以水工模型試驗，以1/70縮尺比例試驗該東堤在增加堤身高度，或拋放消波塊，或使用消波式胸牆，或使用弧形壁堤來作試驗研究何種方式能改善越波情況。
經研究結果認爲堤高至少要加高至10公尺以上，才可有效阻止大部份的越波發生，在海底坡度在1=13至1=10之處易發生碎波，爲減少沖擊到防波堤。拋放消波塊是有其必要，但在坡度太陡之處拋放消波塊很易造成流失。使用弧形壁堤所獲得到防止越波效果最佳，消波胸牆次之，直立壁又次之，拋放消波塊效果最差。
Hwa-Lien harbour is located on the mideast coast of Taiwan and faced Pacific ocean. In this region with great steep bottom slope, there is a lot of typhoon to pass through this area during typhoon season. Therefore, the situation of wave overtopping is very serious before the extension building of lower breakwater has not finished by Hwa Lien harbour bureau. Fortunately, the overtopping is not occurred inside harbour after the fouth period of extension building of lower breakwater has finished. The overtopping in the harbour outside will become in inside that result in effect safety of new wharf built.
In the 1/70 similarity scale of the hydraulic model test for the harbour. It was found that the breakwater height increase to more than ten meters to be able to prevent most of the overtopping occured, and the breakwave often occurs in the bottom slope between 1/13 and 1/10. In order to decrease the breakwave attacting to the breakwater, it is, necessary to set up armor units in the outside of breakwater. But, the steep bottom slope area is difficult to prevent the armor unit loss during the typhoon season. In the results of this study, the orders of efficiency of preventing overtopping from the best to the worst are curved-type breakwater, vertical breakwater with armor unit, vertical breakwater, and armor type only.
