Contents lists available at ScienceDirect Ecological Indicators journal homepage: www.elsevier.com/locate/ecolind Original Articles Vegetative-hydraulic parameters generated by agricultural crops for laminar flows under a semi-arid environment of Pernambuco, Brazil J.R.B. Cantalice a,b, ⁎ , E.O.S. Nunes b , D.M. Cavalcante a , B. Barbosa b,c , G. Barros Junior b , S.M.S. Guerra b , F.C. Rolim Neto b a Soil Conservation Engineering Laboratory, Environmental Engineering Graduate Program of Rural Federal of Pernambuco University, Av. Dom Manuel Medeiros, N/A, 52171900 Recife, PE, Brazil b Environmental Engineering Graduate Program of Rural Federal of Pernambuco University by PNPD/CAPES Brazilian Program, Av. Dom Manuel Medeiros, N/A, 52171900 Recife, PE, Brazil c MEtRiCS, Departamento de Ciências e Tecnologia da Biomassa, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal ARTICLE INFO Keywords: Interrill erosion Vegetal roughness Vegetal cover, drag coefficient Sheet flow ABSTRACT The structural parameters of vegetation have an important influence on the resistance imposed to shallow flow under the soil, being important in the control of floods, water erosion and sediment transport in the watersheds. Therefore, in order to obtain the hydraulic characteristics of overland flow, the variables of hydraulic resistance generated by the vegetation to surface flow, and the interrill erosion rates under semi-arid region led to the introduction of agricultural crops, through which shallow flows were generated on elephant grass (Pennisetum purpureum), corn (Zea mays sp.) and in a bare Entisol, placed in a toeslope landscape position. Results showed that the flow regime was slow, laminar and interrill erosion occurred (Re < 500 and Fr < 1). Nevertheless, the hydraulic characteristics of overland flow (Vm, h, q and log f) were probably affected by the proximity to the water table, a hypothesis supported by the obtained values for the infiltration. However, corn and principally elephant grass showed high hydraulic resistance to superficial flow and interrill erosion conferred by the highest ground coverage (lowest Ci = 0.198), by the effect of the sub-factors CiI, CiII and CiIII, and the lowest values of sediment concentration (CS), runoff coefficient (C), interrill detachment rate (Di), and soil loss (SL). Our results support the purpose of introducing agricultural crops in the Brazilian semi-arid region since increasing resistance to interrill erosion can be provided. Elephant grass is a more appropriate crop to be inserted under land man- agement protocols in the semi-arid environment. 1. Introduction Agricultural activities can intensively affect many natural processes, causing soil erosion that leads to a decrease in soil productivity. Consequently, appropriate agricultural management is fundamental in achieving agricultural sustainability (Liu et al., 2011). Interrill erosion and rill erosion processes are the main concerns to soil erosion on the hillslopes (Balacco, 2013). During the process of interrill erosion, raindrop impacts led to the detachment of soil particles that are then transported by splash and shallow overland flows (Meyer and Harmon, 1979). Shallow flow is associated with interrill erosion, being the result of the intensity of pluviometry event, when the volume of precipitation exceeds the soil infiltration rate after the event has already surpassed all the hydrological removals concerning plant interception, evaporation, soil matrix demand and superficial retention and detention (Bezerra et al., 2010). Hydraulic parameters such as the kinematic viscosity of the water, the mean flow velocity and the water discharge per unit width represent the main physical forces acting on surface flow (Cantalice et al., 2017). Considering the information regarding these hydraulic parameters, other parameters such as the loss load factor, the Reynolds and Froude numbers, and the sheet flow height can be cal- culated (Govers, 2007; Morgan, 1992). Hence, according to Ponce (1989), laminar surface flow can be equated by using the continuity equation in one-dimensional resolution: ∂ ∂ + ∂ ∂ = Q x A t ql (1) where ql is the lateral flow per unit length (m 2 s -1 ); Q is the water discharge (m 3 s -1 ); x is the length in the flow direction (m); A is the https://doi.org/10.1016/j.ecolind.2019.105496 Received 20 November 2018; Received in revised form 27 May 2019; Accepted 18 June 2019 ⁎ Corresponding author. E-mail address: cantalice21@hotmail.com (J.R.B. Cantalice). Ecological Indicators 106 (2019) 105496 1470-160X/ © 2019 Elsevier Ltd. All rights reserved. T