The Secondary Permeability of Impervious Cover

Research Article| November 01, 2008 The Secondary Permeability of Impervious Cover THOMAS J. WILES; THOMAS J. WILES 1Department of Geological Sciences, The Jackson School of Geosciences, 1 University Station, C1100, The University of Texas, Austin, TX 78712-0254 Search for other works by this author on: GSW Google Scholar JOHN M. SHARP, JR JOHN M. SHARP, JR 1Department of Geological Sciences, The Jackson School of Geosciences, 1 University Station, C1100, The University of Texas, Austin, TX 78712-0254 1 Corresponding author: email: jmsharp@mail.utexas.edu; phone: 512-471-3317. Search for other works by this author on: GSW Google Scholar Author and Article Information THOMAS J. WILES 1Department of Geological Sciences, The Jackson School of Geosciences, 1 University Station, C1100, The University of Texas, Austin, TX 78712-0254 JOHN M. SHARP, JR 1 Corresponding author: email: jmsharp@mail.utexas.edu; phone: 512-471-3317. 1Department of Geological Sciences, The Jackson School of Geosciences, 1 University Station, C1100, The University of Texas, Austin, TX 78712-0254 Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online ISSN: 1558-9161 Print ISSN: 1078-7275 © 2008 Association of Engineering Geologists Environmental & Engineering Geoscience (2008) 14 (4): 251–265. https://doi.org/10.2113/gseegeosci.14.4.251 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation THOMAS J. WILES, JOHN M. SHARP; The Secondary Permeability of Impervious Cover. Environmental & Engineering Geoscience 2008;; 14 (4): 251–265. doi: https://doi.org/10.2113/gseegeosci.14.4.251 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Impervious cover signifies buildings, roads, sidewalks, and parking lots of low permeability (assumed nearly zero), and it is a consideration in estimating aquifer recharge in urbanized areas. It is commonly assumed that increasing impervious cover decreases direct recharge from precipitation, but observations of most roads, sidewalks, or parking lots reveal abundant fractures that may permit infiltration. We estimate the secondary permeability of pavements using a double-ring infiltrometer. Linear extrapolation determines the infiltration rate as the water depth approaches zero, which is used as a hydraulic conductivity proxy. Data were collected on pavements in Austin, Texas, at fractures or expansion joints intersected along sixteen 30-meter scan lines. By dividing the sum of the discharges for each fracture by the scan-line area, we determined an equivalent-porous-media hydraulic conductivity. For discrete fractures, these ranged over three orders of magnitude from >10−2 to <10−5 cm/s; scan-line hydraulic conductivities ranged from >10−4 to 10−6 cm/s; permeability along the scan lines tended to be dominated by a few highly conductive fractures; and hydraulic conductivity of the entire paved surface was approximately 5.9 × 10−5 cm/s. By multiplying the paved surface hydraulic conductivity by the time the surface was saturated, we estimate that 21 percent of mean annual rainfall (170 mm) is available as potential recharge. Coupled with enhanced subsurface permeability structure from the installation of utilities and reduction of vegetation and, consequently, evapotranspiration, the net effect of impervious cover on recharge is uncertain, but, in many cases, there is likely either little effect or an increase in recharge from precipitation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.