The purpose of this study was to assess how terracing affected overland flow and associated sediment losses, at the micro-plot scale (0.25 m2 ), in recently burnt stands of the two principal forest types in north-central Portugal, i.e. mono-specific stands of Maritime Pine and Eucalypt. Terracing is an increasingly common practice of slope engineering in the study region but its impacts on runoff and erosion are poorly studied. Non-terraced plots at the Eucalypt and the Pine site revealed similar median runoff coefficients (rc: 20-30%) as well as comparable median sediment losses (15-25 g m-2 ) during the first seven months following wildfire. During the ensuing, slightly wetter 18-month period, however, non-terraced plots at the Pine site lost noticeably more sediments (in median, 90 vs. 18 g m-2 ), in spite the runoff response had remained basically the same (median rc: 33 vs. 28%). By contrast, terraced plots at the same Pine site lost hugely more sediments (in median, 1,200 g m-2 ) during this 18-month period. Terraced plots at the Eucalypt site even lost three times more sediments (in median, 3,600 g m-2 ). Ground cover and resistance to shear stress seemed to be key factors in the observed/inferred impacts of terracing.
The aim of this article is to present partial results of more extensive research which is focused on using different methods for runoff computation in areas differing in land use. With the help of the deterministic lumped model HEC-HMS (Hydrologic Engineering Center - Hydrologic Modelling System) several simulations of runoff changes by different basin conditions were carried out. The Blanice River basin in the Šumava Mts. was chosen as an experimental catchment in its closure profile in Podedvory (gauge station, area 209.6 km2 ). For assessment of land cover changes impact on hydrological regime four scenarios were carried out - 10, 20, 50 and 100-year 1-day probability precipitation in combination with different initial conditions (soil saturation). These scenarios were applied to the stage of the land cover in the year 1992 and 2000 (based on the CORINE Landcover database). The method SCS CN (Soil Conservation Service Curve Number) was applied as the main model technique. and Cílem příspěvku je prezentovat dílčí výsledky rozsáhlejšího výzkumu zaměřeného na změny srážkoodtokového procesu vlivem změn charakteru vegetace a půdního pokryvu. Pomocí matematického modelu HEC-HMS (Hydrologic Engineering Center - Hydrologic Modelling System) byly uskutečněny simulace odtokové odezvy na příčinnou srážku ve dvou časových horizontech, které charakterizují dva odlišné stavy krajinného pokryvu. Modelovou oblastí bylo povodí Blanice po závěrový profil Podedvory (nad VD Husinec, 209,6 km2 ). Reakce povodí na srážkovou událost při změnách vegetačního pokryvu byla zhodnocena ve dvou časových horizontech - 1992 a 2000. K hodnocení změn vegetace byla použita databáze CORINE Landcover. Modelování změny odtokového režimu v daných časových horizontech proběhlo pro čtyři srážkové události. První z nich byl 1-denní úhrn srážek s pravděpodobností překročení 0,1, tedy s dobou opakování 10 let a další s dobami opakování 20, 50 a 100 let. Jako hlavní modelovací technika byla použita metoda SCS CN (Soil Conservation Service Curve Number).