Why could steamboats travel on the lower Rio Grande during the 1850s and 1860s?

During the 1850s and 1860s, small steamboats were able to navigate the lower Rio Grande upstream to Rio Grande City and Roma specifically when the river was high.1

While the river currently experiences significant challenges such as accelerated erosion, silting, and sandbar formation that prevent such navigation, these conditions were not as prohibitive during that period. The ability to travel by steamboat continued until 1874, when a major hurricane swept the river clean of all man-made structures.1