There is certainly a regular Crevasse somewhere over us by the way the rain has been coming down this afternoon. Remained in the house and played whist this evening.
According to the Oxford English Dictionary, crevasse, in the sense Nathan is using it, means a breach in the bank of a river or canal, especially a breach in the levee or artificial bank of the lower Mississippi River.
“crevasse, n.”. OED Online. March 2011. Oxford University Press. http://0-www.oed.com.library.simmons.edu/view/Entry/44336?rskey=mEdD7B&result=1&isAdvanced=false (accessed May 24, 2011).