In a large pot, brown beef until fully cooked; drain.
Stir in the chili powder, flour, salt and garlic powder until blended; gradually stir in water.
Add the beans and bring to a boil. Reduce heat; simmer, uncovered, for 12-15 minutes or until thickened, stirring occasionally.
To serve, divide chips among six serving bowls. Top with beef mixture followed by cheese, tomatoes and onion; garnish with sour cream and cilantro, if desired.