形容词短语作定语，只能放在被修饰词之后，不能之前。这就是所谓的短语、从句作定语，必须是“后置定语”。

parallel to shore 确实是一个“形容词短语”，意为：与海岸平行的。在本句作状语，修饰动名词 building，说明建造 a breakwater of rocks 的位置地点。状语提到宾语之前的原因是：宾语太长，照顾匀称。

In a plan to stop the erosion of East Coast beaches, the Army Corps of Engineers proposed building parallel to shore （building 的状语）a breakwater of rocks （building 的宾语）that would rise six feet above the waterline and act as a buffer, absorbing the energy of crashing waves and protecting the beaches.