Thanks, that&#x27;s exactly it.  Some tetrapods are effective against erosion control.  But, just because they are effective does not mean they are needed everywhere nor is it clear we need to protect all places which do suffer erosion.  It&#x27;s a natural process -sometimes we want to curtail it, sometimes not.  In Japan, it&#x27;s almost always unquestionably &quot;a good&quot; specially when considered by the concrete industrial retirement complex.