Just a little story to add
One of my colleagues regularly has to make trips to Dallas and prefers to say in a Marriot resplendence facilities for her extended stays. She had done this for many years without any problems. After Katrina the place was flooded with "refugees" from NO.
Her room was robbed. All of her belongings were taken. Clothes, laptop, everything right down to her tooth brush. The very apologetic manager could only offer "I am sorry, but since we took in the Katrina evacuees all of our rooms have been robbed."
I have read your OP link. You miss understand the point of the article. What is being said is that there is no long term criminal problems due to the evacuees.
They are very up front that there was a crime problem attributed to the "evacuees" upon arrival to their new "temporary" homes. These are quotes from the OP link.
What we found in Houston was there appears to be an increase in some categories of crime, in particular murder and robbery, during the Katrina time period when the evacuees came to Houston."
We did have an initial spike, but then things did settle down when we got a handle on it, said Andy Kahan, Houston's crime victims advocate."
"The study examined weekly crime reports in the three cities from January 2004 to September 2006, and found there were increases in certain categories of crime after the storm."
Could the leveling our of crime be that many of them have gone home or moved? Been arrested? Or that the local criminals took care of the problem themselves?
There is no denying that the crime rates in many places jumped due to the influx of Katrina "evacuees."