Dynamic runoff connectivity of overland flow on steep forested hillslopes: Scale effects and runoff transfer

[1] Both scaling effect and connectivity of overland flow were examined in steep hillslopes covered by (1) Japanese cypress (hinoki, Chamecyparis obtusa) plantations with sparse understory vegetation, (2) hinoki plantations with fern understory vegetation, and (3) deciduous forests. Two sizes of plots were installed for monitoring overland flow: small (0.5 × 2 m) and large hillslope scale (8 × 24–27 m). For all hillslopes, measurable amounts of overland flow occurred during storms. Runoff coefficients of large plots (0.1–3%) were consistently smaller than those of small plots (20–40%). Estimated runoff flow lengths at the hillslope scale were based on runoff coefficients from small plots and were used to calculate runoff volume from large plots. Then we compared the differences between observed and estimated runoff volumes of large plots. Estimated runoff from large plots was smaller than observed runoff in hinoki slopes with sparse understory vegetation. Greater amounts of observed compared to estimated overland flow suggest that more runoff occurred from hillslopes with sparse understory. In contrast, estimated overland flow was larger than observed runoff from the deciduous forest, implying greater opportunities for infiltration compared to hinoki hillslopes. Comparison of estimated versus observed overland flow for successive 5 min intervals during storms indicates that runoff networks expand upslope during short and intense precipitation periods. Our examination and comparison of storm runoff from small and large plots facilitate better understanding of runoff mechanisms, scaling effects in hillslopes, and connectivity of the overland flow network.

[1]  R. Shakesby,et al.  Soil water repellency as a potential parameter in rainfall‐runoff modelling: experimental evidence at point to catchment scales from Portugal , 2003 .

[2]  John Wainwright,et al.  The effect of temporal variations in rainfall on scale dependency in runoff coefficients , 2002 .

[3]  A. El-Hassanin,et al.  Effect of vegetation cover and land slope on runoff and soil losses from the watersheds of Burundi , 1993 .

[4]  M. Bonell,et al.  The influence of scale of measurement on the spatial and temporal variability of the Philip infiltration parameters — An experimental study in an an Australian savannah woodland , 1988 .

[5]  A. Yair.  The Control Of Headwater Area On Channel Runoff In A Small Arid Watershed , 1992 .

[6]  T. Dunne,et al.  Effects of Rainfall, Vegetation, and Microtopography on Infiltration and Runoff , 1991 .

[7]  A. Parsons,et al.  Impact of connectivity on the modeling of overland flow within semiarid shrubland environments , 2007 .

[8]  Karin Laursen,et al.  A conceptual model of preferential flow systems in forested hillslopes: evidence of self‐organization , 2001 .

[9]  A. Joel,et al.  Measurement of surface water runoff from plots of two different sizes , 2002 .

[10]  Hanoch Lavee,et al.  Overland flow generation and continuity on stone‐covered soil surfaces , 1991 .

[11]  J. Letey,et al.  Indices for Characterizing Soil-Water Repellency Based upon Contact Angle-Surface Tension Relationships , 1970 .

[12]  Murugesu Sivapalan,et al.  Spatial Heterogeneity and Scale in the Infiltration Response of Catchments , 1986 .

[13]  K. Beven,et al.  Scale effects in infiltration and runoff production , 1986 .

[14]  A. C. Imeson,et al.  The effects of fire and water repellency on infiltration and runoff under Mediterranean type forest , 1992 .

[15]  N. C. Van de Giesen,et al.  Scale effects of Hortonian overland flow and rainfall–runoff dynamics in a West African catena landscape , 2000 .

[16]  John Wainwright,et al.  Scale relationships in hillslope runoff and erosion , 2006 .

[17]  P. Møldrup,et al.  Soil water repellency: effects of water content, temperature, and particle size , 1999 .

[18]  I. Cordery,et al.  Formation of runoff at the hillslope scale during intense precipitation , 2006 .

[19]  R. Sidle,et al.  Understanding Processes and Downstream Linkages of Headwater Systems , 2002 .

[20]  R. Horton.  The Rôle of infiltration in the hydrologic cycle , 1933 .

[21]  V. Chaplot,et al.  Field measurements of interrill erosion under ­different slopes and plot sizes , 2000 .

[22]  P. Germann,et al.  Investigations on the runoff generation at the profile and plot scales, Swiss Emmental , 2006 .

[23]  Ian Cordery,et al.  Estimation of interception capacity of the forest floor , 1996 .

[24]  L. H. Cammeraat.  A review of two strongly contrasting geomorphological systems within the context of scale , 2002 .

[25]  D. Levia,et al.  A review and evaluation of stemflow literature in the hydrologic and biogeochemical cycles of forested and agricultural ecosystems , 2003 .

[26]  C. K. Mutchler,et al.  Effect of Slope Length on Erosion from Low Slopes , 1980 .

[27]  O. Slaymaker,et al.  Identification, characterization, and hydrological implications of water repellency in mountain soils, southern British Columbia , 1989 .

[28]  C. Gascuel-Odoux,et al.  Evolution of soil surface roughness and flowpath connectivity in overland flow experiments , 2002 .

[29]  J. Buttle,et al.  Runoff processes on a forested slope on the Canadian shield , 1999 .

[30]  A. J. Parsons,et al.  Distribution of depth of overland flow on desert hillslopes and its implications for modeling soil erosion , 1989 .

[31]  K. Nanko,et al.  Estimation of soil splash detachment rates on the forest floor of an unmanaged Japanese cypress plantation based on field measurements of throughfall drop sizes and velocities , 2008 .

[32]  R. Bryan,et al.  The influence of slope angle on final infiltration rate for interrill conditions , 1997 .

[33]  R. Sidle,et al.  Hortonian overland flow from Japanese forest plantations—an aberration, the real thing, or something in between? , 2007 .

[34]  Pierre Y. Julien,et al.  Similarity and length scale for spatially varied overland flow. , 1990 .

[35]  Tammo S. Steenhuis,et al.  Scale effects of Hortonian overland flow and rainfall‐runoff dynamics: laboratory validation of a process‐based model , 2002 .

[36]  K. D. Sharma.  Runoff behaviour of water harvesting microcatchments , 1986 .

[37]  A. Nik,et al.  Characteristics of spatial distribution of throughfall in a lowland tropical rainforest, Peninsular Malaysia , 2006 .

[38]  I. D. Moore,et al.  Estimating Micro-Relief Surface Storage from Point Data , 1979 .

[39]  John Wainwright,et al.  A conceptual model for determining soil erosion by water , 2004 .

[40]  H. Elsenbeer,et al.  Overland flow generation in two lithologically distinct rainforest catchments , 2004 .

[41]  L. Stroosnijder,et al.  Matching hydrologic response to measured effective hydraulic conductivity , 2006 .

[42]  Juan B. Valdés,et al.  On the influence of the spatial distribution of rainfall on storm runoff , 1979 .

[43]  T. Gomi,et al.  Surface runoff as affected by soil water repellency in a Japanese cypress forest , 2007 .

[44]  J. Poesen.  Mechanisms of overland-flow generation and sediment production on loamy and sandy soils with and without rock fragments , 1992 .

[45]  Takanori Shimizu,et al.  Soil water repellency in a Japanese cypress plantation restricts increases in soil water storage during rainfall events , 2007 .

[46]  Shoji Noguchi,et al.  Stormflow generation in steep forested headwaters: a linked hydrogeomorphic paradigm , 2000 .

[47]  M. Sharma,et al.  Spatial variability of infiltration in a watershed , 1980 .

[48]  R. Lal.  Effects of slope length on runoff from alfisols in Western Nigeria , 1983 .

[49]  Olivier Cerdan,et al.  Scale effect on runoff from experimental plots to catchments in agricultural areas in Normandy , 2004 .

[50]  I. Moore,et al.  Soil hydrophobic effects on infiltration and catchment runoff , 1989 .

[51]  R. Shakesby,et al.  Spatial variability of soil hydrophobicity in fire-prone eucalyptus and pine forests, Portugal , 1998 .

[52]  Felix Naef,et al.  An experimental tracer study of the role of macropores in infiltration in grassland soils , 2003 .

[53]  John Wainwright,et al.  Resistance to overland flow on semiarid grassland and shrubland hillslopes, Walnut Gulch, southern Arizona , 1994 .

[54]  Thomas W. Giambelluca,et al.  Runoff generation and sediment production on unpaved roads, footpaths and agricultural land surfaces in northern Thailand , 2000 .

[55]  Jean Poesen,et al.  Laboratory experiments on the influence of slope length on runoff, percolation and rill development , 1989 .