“Colonia” is like sayin slum or ghetto, in Spanish.
The article you linked discusses their vulnerability to flooding, but one of the major benefits of the new border wall, is that in the parts of the Valley vulnerable to flooding (around McAllen, and East to the Gulf), The barrier is built as an upgrade to the levees - to FEMA hurricane specs. It is a huge infrastructure boost for the area, that otherwise might wait decades for funding.
Demographically, that area is overwhelmingly packed with Spanish speakers, because of immigration. Nearby Laredo is the least diverse city in the United States - over 95% Hispanic.