Next Article in Journal
Comparing One-Way and Two-Way Coupled Hydrometeorological Forecasting Systems for Flood Forecasting in the Mediterranean Region
Next Article in Special Issue
Determination of Watershed Infiltration and Erosion Parameters from Field Rainfall Simulation Analyses
Previous Article in Journal
Impact of Climate Change on Groundwater Resources in the Klela Basin, Southern Mali
Previous Article in Special Issue
Soil Erosion Processes in European Vineyards: A Qualitative Comparison of Rainfall Simulation Measurements in Germany, Spain and France
Article Menu

Export Article

Open AccessArticle
Hydrology 2016, 3(2), 18; doi:10.3390/hydrology3020018

Surface Runoff in Watershed Modeling—Turbulent or Laminar Flows?

Hydrologic Sciences and Biological & Agricultural Engineering, UC Davis, Davis, CA 95616, USA
Academic Editors: Thomas Iserloh, Artemi Cerdà, Wolfgang Fister and Saskia Keesstra
Received: 5 April 2016 / Revised: 20 April 2016 / Accepted: 25 April 2016 / Published: 4 May 2016
View Full-Text   |   Download PDF [5288 KB, uploaded 4 May 2016]   |  

Abstract

Determination of overland sheet flow depths, velocities and celerities across the hillslope in watershed modeling is important towards estimation of surface storage, travel times to streams and soil detachment rates. It requires careful characterization of the flow processes. Similarly, determination of the temporal variation of hillslope-riparian-stream hydrologic connectivity requires estimation of the shallow subsurface soil hydraulic conductivity and soil-water retention (i.e., drainable porosities) parameters. Field rainfall and runoff simulation studies provide considerable information and insight into these processes; in particular, that sheet flows are likely laminar and that shallow hydraulic conductivities and storage can be determined from the plot studies. Here, using a 1 m by 2 m long runoff simulation flume, we found that for overland flow rates per unit width of roughly 30–60 mm2/s and bedslopes of 10%–66% with varying sand roughness depths that all flow depths were predicted by laminar flow equations alone and that equivalent Manning’s n values were depth dependent and quite small relative to those used in watershed modeling studies. Even for overland flow rates greater than those typically measured or modeled and using Manning’s n values of 0.30–0.35, often assumed in physical watershed model applications for relatively smooth surface conditions, the laminar flow velocities were 4–5 times greater, while the laminar flow depths were 4–5 times smaller. This observation suggests that travel times, surface storage volumes and surface shear stresses associated with erosion across the landscape would be poorly predicted using turbulent flow assumptions. Filling the flume with fine sand and conducting runoff studies, we were unable to produce sheet flow, but found that subsurface flows were onflow rate, soil depth and slope dependent and drainable porosities were only soil depth and slope dependent. Moreover, both the sand hydraulic conductivity and drainable porosities could be readily determined from measured capillary pressure displacement pressure head and assumption of pore-size distributions (i.e., Brooks-Corey lambda values of 2–3). View Full-Text
Keywords: rainfall-runoff modeling; runoff simulations; laminar or turbulent flows; travel times; hillslope drainage rainfall-runoff modeling; runoff simulations; laminar or turbulent flows; travel times; hillslope drainage
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Scifeed alert for new publications

Never miss any articles matching your research from any publisher
  • Get alerts for new papers matching your research
  • Find out the new papers from selected authors
  • Updated daily for 49'000+ journals and 6000+ publishers
  • Define your Scifeed now

SciFeed Share & Cite This Article

MDPI and ACS Style

Grismer, M.E. Surface Runoff in Watershed Modeling—Turbulent or Laminar Flows? Hydrology 2016, 3, 18.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Hydrology EISSN 2306-5338 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top