LEWIS AND CLARK'S GEOMORPHIC AND HYDROLOGIC OBSERVATIONS AND 200 YEARS OF CHANGE

Most people think of Meriwether Lewis and William Clark as explorers, but they were also scientists who led one of the first scientific expeditions, Corps of Discovery, across the United States. Both men were keen observers and provided early insights into the yet unnamed fields of geomorphology and hydrology. After long days in the field, they also found time to write down their observations in spite of the troublesome mosquitoes and limitations not experienced today by most scientists. Meriwether Lewis was the biologist/botanist who wrote in a narrative and descriptive style that can transport the reader back 200 years. William Clark was the mapmaker/riverman who wrote facts in a refreshing style punctuated with capitalization for emphasis and who used novel but phonetically correct spellings. Both of their journal entries show impressive insights into geomorphology and hydrology, some of which have been verified 150-200 years later. One primary geomorphic contribution of the expedition was the creation of detailed maps of the network of rivers and landforms. Adjectives they used to describe the landforms they encountered are found today in the standard names of the subdivisions of physiographic provinces. They provided some of the first descriptions of flood plains and other geomorphic features in the United States and how erosion, sediment transport, and deposition altered these features. They measured the rise and fall of rivers, which can be related, in some situations, to their temperature measurements. For many streams and rivers they recorded the navigability, water color, saltiness, and the size of the bed material. They accurately measured the width of every stream they encountered, from four yards wide up to rivers wider than a thousand yards. They made the first velocity measurements of most of the major rivers they encountered and provided some of the first descriptions, excellent even by modern standards, of turbulent processes in these rivers. It is unfortunate that the journals were not published until the late 1800s because these astute observations and simple measurements may have spurred others into similar investigations that would have provided us with, perhaps, 50-70 years of additional historical data to use in understanding natural riverine systems before humans began to alter and control these systems.