Interrill erosion and roughness parameters of vegetation in rangelands J.R.B. Cantalice a, ⁎, F.P.M. Silveira a , V.P. Singh b , Y.J.A.B. Silva a , D.M. Cavalcante a , C. Gomes a a Soil Conservation Engineering Laboratory, Agronomy Department, Rural Federal of Pernambuco University (UFRPE), Recife, PE, Brazil b Biological and Agricultural Engineering Department, Civil and Environmental Engineering Department, Texas A & M University, College Station, TX, USA abstract article info Article history: Received 24 August 2015 Received in revised form 21 March 2016 Accepted 24 April 2016 Available online xxxx In recent decades, the micro-region of Paraiba state, Brazil, has been undergoing the process of replacing its native coverage by crops, mainly pastures for grazing. This land use change has led to the detachment of soil due to the water erosion. Thus, this research had the merit of analyzing the hydraulic roughness parameters generated by pasture emergent vegetation in field condition under interrill erosion. This study was conducted in a randomized block with 4 treatments and 5 replicates, totaling 20 experimental plots. The treatments com- prised different slopes (15%, 25%, 35% and 45%) in an Ultisol. The mean flow velocity and the rate of infiltration in the pasture varied significantly with the increase in slope, contributing to increasing erosion rates until 35% slope. For the slope equal to 45%, the largest soil loss was not observed, chiefly because the crop covers offset the effects generated by the increase in the slope and also due to the remotion of surface horizon (A horizon) which was removed by previous water erosion, which now acted directly on the B horizon. The vegetation drag coefficient (C D ′) of the pasture exhibited an increase when occurred a reduction of turbulent flow between plants. In the condition of increasing in flow depth (h) there was a greater energy flux between the mass of water and the plant structure of Brachiaria decumbens that resulted in the decrease of the vegetation resistance force (Fdrag). © 2016 Elsevier B.V. All rights reserved. Keywords: Soil detachment Vegetation resistance force Brachiaria decumbens Vegetation drag coefficient Runoff coefficient 1. Introduction The erosion of soil by the flow water begins as interrill erosion which occurs due to a combination of two different processes: detachment of soil due to the action of raindrops on soil and interrill flow that can transport of the detached soil by overland flow, often called shallow laminar flow (Everaert, 1991; Nearing, 1997; Zartl et al., 2001; Cassol et al., 2004; Foltz et al., 2009; Govers, 1996). Three factors that are strongly related to interrill erosion: runoff, rainfall intensity and the angle of inclination of the surface that directly affects the detachment processes and transport. With the increase in the degree of slope, the flow velocity increases the power of flow and the movement of these preferred detached particles downward slope, thereby increasing the erosive potential (Assouline and Ben-Hur, 2006; Armstrong et al., 2011). Estimating the flow resistance of vegetation is of great importance in river management, since it may have a significant effect on the convey- ance of the channel. Indeed, the presence of vegetation has traditionally been regarded as a problem which hinders flow capacity. However, it is well known that vegetation has fundamental ecological functions in the riverine environment. Thus, current environmental river engineer- ing prefers to preserve natural riverbank and floodplain vegetation. Fur- thermore, river restoration and rehabilitation are widely practiced. In addition, there is an increased interest in application of various bioengi- neering methods. Thus, in order to cope with new management objectives a better knowledge of the hydraulic effects of vegetation is required (Jarvela, 2002). Still, Jarvela (2002) said that flow resistance problems are usually classified into two groups: flow over submerged, short vegetation and flow through nonsubmerged, tall vegetation. Most efforts to study vegetal resistance have concentrated on studying submerged and rigid roughness. Less is known about the effects of flexible roughness and alterations in flow depth. There is only little avail- able field data other than overall roughness coefficients representing limited flow conditions. The presence of vegetation alters the velocity field across several scales, ranging from individual branches and blades on a single plant to a community of plants in a meadow or patch. Flow structure at the different scales is relevant to different processes (Neft, 2012). Thus, the retention or release of organic matter, mineral sediments, seeds, and pollen from a meadow or patch depends on the flow structure at the meadow or patch scale (Zong and Nepf, 2010). The vegetation plays an important role in the behavior of runoff to offer resistance to its movement due to a set of attributes, the most im- portant are the shape of the plant, size, stiffness, diameter, height, distri- bution, plant density and degree of submergence (Lee et al., 2004; Catena xxx (2016) xxx–xxx ⁎ Corresponding author at: Soil Conservation Engineering Laboratory, Agronomy Department of Rural Federal of Pernambuco University, Av. Dom Manuel Medeiros, NA, 52171900, Recife, PE, Brazil. E-mail address: Cantalice21@hotmail.com (J.R.B. Cantalice). CATENA-02799; No of Pages 6 http://dx.doi.org/10.1016/j.catena.2016.04.024 0341-8162/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Catena journal homepage: www.elsevier.com/locate/catena Please cite this article as: Cantalice, J.R.B., et al., Interrill erosion and roughness parameters of vegetation in rangelands, Catena (2016), http://dx.doi.org/10.1016/j.catena.2016.04.024