Some general observations of physiographic and climatic influences on floods

Abstract

The magnitude of flood‐runoff and the degree to which it concentrates in river‐channels with respect to time is known to vary within wide limits. To a considerable extent these variations relate to the physiographic and edaphlc features of the drainage‐basins as they have been developed by the geologic and climatic history of the particular province in which they are located. Although storms of high intensity occur throughout the United States, the runoff therefrom has been observed to have certain inherent characteristics in wet or humid areas that are different from those in arid or semiarld regions even though the laws governing the flow of water either over ground or in river‐channels are universal in application. Essential features of flood‐behavior in wet or humid areas where stream‐flow is sustained throughout the year and river‐channels and valleys are comparatively well defined and permanent, differ from those in arid or semiarld regions where stream‐flow is very erratic and flashy and the channels are formed largely by occasional intense runoff rather than the slow and orderly development by the continuous occupancy by flowing water. Moreover the flood‐problem in areas where a part of the precipitation occurs as snow differs from that in areas where all the precipitation occurs as rain. Furthermore, in areas where snow does occur there seems to be a wide range in flood‐runoff characteristics depending upon the temperature in and altitude of the particular zone. Some of the different flood‐characteristics as they relate to total runoff and the concentration thereof are described herein and possible reasons therefor are related to conditions which seem to be more or less inherent in particular physiographic and climatic provinces.

Spatial distribution of the largest rainfall‐runoff floods from basins between 2.6 and 26,000 km2 in the United States and Puerto Rico

“…However, within these broad areas, the largest unit discharges apparently owe to combined effects of specific topographic conditions, such as basin relief, basin shape and aspect, drainage network structure, and basin substrate, that can influence rainfall volumes and distribution within a basin as well as the speed and efficiency in which the rainfall is routed through the channel network. This observation has been postulated generally [e.g., Horton , 1932; Hoyt and Langbein , 1939] and demonstrated for individual extreme floods [e.g., Baker , 1977; Smith et al , 1996; Sturdevant‐Rees et al , 2001], and is corroborated by the national view of high unit discharges provided by extensive USGS flow records.…”

Evapotranspiration: A process driving mass transport and energy exchange in the soil‐plant‐atmosphere‐climate system

“…Not surprisingly then, this link has been the subject of some 60 years of research [ Gleick , 1989]. The approaches followed now are rooted in the pioneering work of Langbein, who was among the first to connect climatic fluctuations to runoff fluctuations via ET [ Hoyt and Langbein , 1939; Langbein , 1949]. Large increases in R o have been reported for the period spanning 1901–1999 [ Labat et al , 2004; Manabe et al , 2004a, 2004b; Milly et al , 2005; Peterson et al , 2002; Piao et al , 2007].…”

Where Is the Rain-on-Snow Zone in the West-Central Washington Cascades?: Monte Carlo Simulation of Large Storms in the Northwest

“…Gerdel (1945Gerdel ( , 1948a and other hydrologists appeared in proceedings of the American Geophysical Union Hydrology Section, the Western Interstate Snow Survey Conference (later Western Snow Conference), and international publications. A particular focus of attention was the role of ROS in flooding in the U.S., especially in mid-elevation mountain regions of the West (Jarvis, 1939;Hoyt and Langbein, 1939;Parsons, 1940; P.E. Church, 1940).…”

“…The geographic scope and variability of ROS is suggested by regional and global inventories of flooding and mass movement, in which the attribution of impacts to ROS has been limited but is increasing. Compendia of floods (Jarvis, 1939;Hoyt and Langbein, 1939;Matthai, 1990;Costa, 2003, 2004;Ashley and Ashley, 2008a,b) commonly classify rainfall and snowmelt as separate causes; they mention combined rain plus snowmelt less frequently, and those chiefly due to spring/summer storms in high mountains such as the Alps and Himalayas. Similarly, in compilations of landslide occurrence (Eisbacher and Clague, 1984;Brabb and Harrod, 1989;Schuster and Highland, 2001), reference to rain plus snowmelt as a triggering mechanism has been uncommon.…”