This grass is known as bushy bluestem. You may notice there are many species of grasses referred to as "bluestem" such as big bluestem, little bluestem, cane bluestem, etc. Bushy bluestem is a stout, coarse grass that grows in soggy areas. It's fairly unmistakable by its bushy inflorescence and almost sedge-like apprearance. It's not very palatable to cattle so they tend to avoid it and it subsequently takes over pastures. You'll see tons of it along FM 2351 as you approach I-45. The dead stalks hang around for a long time.
I should mention the last photograph was taken at the Armand Bayou Nature Center in Pasadena where they have restored a large acreage of Texas coastal prairie.