The Canadian Association of Geographers recently held a special session on Changing Priorities in Physical Geography (I did not attend or participate; I was made aware of it by a Canadian colleague). The session description is given here. It got me to thinking about a piece I wrote more than a decade ago in response to a similar mandate, called Laws, Contingencies, and Irreversible Divergence in Physical Geography. I thought I would revisit what I published back in 2004 to see how it holds up. The paper focused on physical geography as science and scholarship, as opposed to the institutional politics of physical geography within geography as a whole, and relative to other disciplines. However, I did predict that physical geography—as geomorphology, climatology, biogeography, soil geography, and geospatial approaches to Earth & environmental sciences—would grow and thrive. However, I also expressed doubt that this work would continue to be called physical geography, and the extent to which it would be conducted under the institutional auspices of geography.

Tobias Heckmann, Wolfgang Schwanghart and I recently published the second of our two articles on applications of graph theory in physical geography & geosciences: Graph Theory—Recent Developments of Its Applications in Geomorphology (Geomorphology, v. 243, p. 130-146).  The other paper, an overview of graph theory in geosciences, was promoted in this post.

Example of a structural graph, from the article. 

Just finished John Brooke’s Climate Change and the Course of Global History: A Rough Journey (Cambridge University Press, 2014). If nothing else, the book is a remarkable achievement with respect to the breadth and depth of literature and ideas brought to bear, including history, geography, geology, anthropology, economics, climatology, ecology, and archaeology. Brooke also makes a compelling case for a significant role for environmental change in general, and climate change in particular, in influencing human affairs and history (and, of course, vice-versa).

As I write, there is flooding in central Texas, and more to come. The focus is rivers and creeks in the San Antonio and Guadalupe River systems in the Balcones Escarpment area along the San Antonio-Austin Corridor, with effects beginning to felt downstream.

Destroyed trees along banks of the Blanco River, Wimberly, TX, after the flood of 24 May, 2015 (photo by Jay Janner, Associated Press).

The Froude number is a hydraulic parameter often used to relate aquatic habitats and biotopes to flow intensity. Independently of some trenchant critiques (see, e.g., Clifford et al. 2006), there seems to be no inherent hydrological, geomorphological, or ecological reason that the Froude number (Fr) should be the best indicator of habitat or ecological niches.

Fr is a dimensionless number that describes flow regimes in open channels and is unquestionably useful in many aspects of hydrology, geomorphology, and engineering. It is the ratio of inertial and gravitational forces:

Fr = V/(g d)^0.5

Fr < 1 indicates subcritical or tranquil, and Fr > 1 supercritical or rapid flow. But variations in Fr within the subcritical range (where it typically falls) can be significantly related to, e.g., geomorphic units and habitats within channels.

Shawnee Run, Kentucky