The <a href="https://en.wikipedia.org/wiki/Great_Mississippi_Flood_of_1927" class="extiw" title="en:Great Mississippi Flood of 1927">Great Mississippi Flood of 1927</a>, dynamiting through the levee to create an artificial crevasse at Caernarvon, <a href="https://en.wikipedia.org/wiki/St._Bernard_Parish,_Louisiana" class="extiw" title="en:St. Bernard Parish, Louisiana">St. Bernard Parish, Louisiana</a>, 14 miles below <a href="//commons.wikimedia.org/wiki/New_Orleans" title="New Orleans">New Orleans</a>.  The crevasse was created to take pressure off levees at New Orleans.
Archival Photography by Steve Nicklas, NOS, NGS
1927
<a rel="nofollow" class="external text" href="http://www.photolib.noaa.gov/historic/nws/wea00739.htm">wea00739, Historic NWS Collection</a>, <a rel="nofollow" class="external autonumber" href="http://www.photolib.noaa.gov/historic/nws/images/big/wea00739.jpg">[1]</a>