I would google for the various if not nearly endless reports from various magazines on the best places for retirement. It is a very mixed bag depending on the variables and criteria used and weight used. I don't remember Sioux Falls making any of those lists. Lincoln, NB, in that area has made some lists and is every more central and less prone to flooding. Lincoln mades the list generally for good health facilities, university town, and low housing costs. My first thought is that the connection between those little airport and major hubs can be very limited and expensive.
Having grown up in the sandhills of Nebraska and university in Iowa, Sioux Falls or that area would not be high on my list as a retirement community. Hot and humid in the summer and cold and windy in the winter. Not sure when the weather is good.
PS -- I would not retire to Lincoln either but it has been some lists.