How to remove crawfish from your yard?

Soil drainage is the best method where legal, however if your yard is considered wetlands it would result in huge fines and you'd also have to restore the wetland to its original state. To make matters worse crawfish may be protected by law in some states.

A Texas golf course buried galvanized cloth wire, but it sounds like a lot of work for your yard. The website with that mentions some illegal and toxic ways so I'll only post the part about the wire giving credit to the individuals who gave it to them.

"We are indebted to Mr. C. K. Anderson, President of the Ridgemoor Country Club, Norwood Park, Illinois, for the following account of the successful control of crawfish by means of wire cloth buried underneath the turf, so as to prevent the crawfish from coming up from beneath and destroying the greens. Mr. Anderson informs us that the material used was 3 by 3 mesh No. 16-gauge wire cloth galvanized after weaving. It was employed by Mr. J. E. Millikin on a golf course at Orange, Texas. In a letter to Mr. Anderson, Mr. Millikin writes as follows: "This wire cloth will be placed 16 to 18 inches under the top of our greens and below the grass roots, and will extend under the bunkers bordering the greens, laid down the entire width or breadth of the green, lapped 2 inches and wired about every three feet to hold in place. Numerous other ideas have been tried to eliminate the crawfish, such as cinders, gravel, and iron chips, but the hardware cloth is about the only thing that the writer knows of which has proved successful."

Crawfish? If we're talking about the same creature, you boil them alive and eat them with corn, potatoes, sausage and lots of spices. But I don't think those kind of crawfish live in yards... are you sure that's what you mean?

HMM...... is your yard completely covered in water? You sure you having a crawfish problem? No water no crawfish!