Effects of urbanization on watershed hydrology: The scaling of discharge with drainage area

Abstract

Galster et al. (2006) use questionable data for two Pennsylvanian streams to misconstrue the dependence of streamfl ow on watershed area and urbanization. Their fi rst equation, Q = kA c , relates fl ow rate 'Q' (m 3 /s) to drainage area 'A' (m 2), using 'k,' "a measure of river base fl ow (m/s)" and 'c', "the scaling power dependency" (Galster, et al., 2006, p. 713) Their Table 3 reports both positive and negative values for k, and redefi nes its units as m 3 /s. Instead, Equation 1 requires that k be positive because both Q and A are positive, and that k has inconsistent units that depend on c. Because Table 3 reports that c ranges from 0.32 to 1.61 for different hydrographs in Sacony Creek (cf. Figure 1), k's units must vary from m +2.36 /s to m-0.22 /s. Such implausible and inconsistent units are one of many problems that arise when empirical relationships and log-log plots are misused in hydrology. The values Galster et al. list for k in Table 3, e.g.,-2.25 to +1.37 for Sacony Creek, actually are values of log k. Because the scale is logarithmic, this represents a >4,000 fold range for k, rendering it useless as a measure of base fl ow. Also, the various fi ts of Equation 1 to their data are poor and confl icting (Figure 1). Dates of occurrence are not reported for most discharge events used by Galster et al., and when they are, inconsistencies abound. Their Figure 2 caption states that the results are for "December 2004 to January 2005," yet their x-axis encompasses only June and July, 2005. None of the points shown in Figure 2 correspond in any way to Table 3, which is referenced

Quantifying river form variations in the Mississippi Basin using remotely sensed imagery

“…3). A linear relationship between upstream drainage area and discharge has been commonly assumed in small basins (e.g., Pazzaglia et al, 1998;Montgomery and Gran, 2001), but for larger rivers this relationship may become nonlinear if the basin includes variations in geology, tectonic deformation, climate, or land use (Stall and Fok, 1968;Galster et al, 2006;Tague and Grant, 2004). To account for these variations, we developed discharge-drainage area relationships for individual sub-basins using values of discharge and drainage area for all USGS stations with ≥ 10 years of approved mean annual discharge.…”

Penetration of ultraviolet radiation in streams of eastern Pennsylvania: Topographic controls and the role of suspended particulates

“…Land use can also change the concentration and/or optical quality of dissolved organic carbon (DOC) transported from the watershed (Frost et al, 2005). Conversion of forest to agricultural or urban land use, for example, can change the quantity and grain size distribution of sediment contributed to the stream (Kondolf et al, 2002), which has implications for stream channel morphology (Leopold et al, 1964;Pizzuto et al, 2000;Galster et al, 2006). For example, transition to a wider, shallower channel increases UVR exposure on the benthos.…”

“…For example, transition to a wider, shallower channel increases UVR exposure on the benthos. Loss of riparian vegetation can have the direct effect of causing an instantaneous, localized increase in UVR flux reaching the stream (DeNicola et al, 1992;Kelly et al, 2003;Brown et al, 1994) or indirectly increase benthic exposure to UVR through bank destabilization (Hession et al, 2003), which could also lead to channel widening and shallowing (Galster et al, 2006). Current lack of understanding of how upland hillslope form and geomorphic process influence many of the environmental parameters that influence UVR transparency is a critical limitation on the development of broadly applicable, predictive models of UVR penetration in streams.…”

Evaluating a Great Lakes scale landscape stressor index to assess water quality in the St. Louis River Area of Concern

“…Human development of watersheds, particularly urbanization and agriculture, has a strong impact on the quality and ecological functions of aquatic systems (Booth and Jackson, 1997;King et al, 2005;Galster et al, 2006;Brown et al, 2009;Johnson and Host, 2010). Urbanization is typically positively correlated with the concentrations and loads of many contaminants, including nutrients, sediments, heavy metals, petroleum products, salts, fecal indicator bacteria, organic contaminants and others (Paul and Meyer, 2001).…”