Later waves are never weaker than the former.
or
Waves which come later are stronger and higher.
英文的谚语很少有直译的,因为人家那里根本没有长江啊,所以只能用普遍的意思与之对应.
如果还不满意,那就爱莫能助啦:
As in Yangtze River,it's the inferior waves that push the former waves.