"Based on what studies do exist, the analysts say that building and
maintaining a fence through the remote or hostile terrain along the
border would run into billions of dollars, with no documented impact on
diminishing illegal crossings. ... Richard F. Cortez, the mayor of the Texas border town of McAllen, noted
that much of the state’s border is defined by rivers. “It is a winding
river,” Mr. Cortez, a political independent, said in an interview on
Wednesday. “Where in the world are you going to put fencing? To propose
that suggests ignorance of the border and the terrain.”"
Julia Preston, New York Times, Oct. 20, 2011.