Complex sentence: Deforestation of the river banks in the 19th century to fuel steamboats had dramatic environmental effects in this region, leading to the Mississippi River between St. Louis and the confluence with the Ohio River becoming more wide and shallow, as unstable banks collapsed into the water.
Split into simpler sentences: Deforestation of the river banks in the 19th century to fuel steamboats had dramatic environmental effects in this region. The Mississippi River between St. Louis and the confluence with the Ohio River became wider and more shallow, as unstable banks collapsed into the water.