Laboratory apparatuses for the analysis of infiltration and runoff enable studies under controlled environments and at reduced costs. Unfortunately, the design and construction of such systems are complex and face difficulties associated with the scale factor. This paper presents the design, construction, and evaluation of a portable rainfall and runoff simulator. The apparatus allows the evaluation of unsaturated soils with and without vegetation cover, under a wide range of simulation scenarios. The apparatus also enables the control of the intensity, size, and uniformity of simulated raindrops for variable surface slope, specimen thickness, and length conditions. The monitoring of the volumetric water content and matric suction and a rigorous computation of water balance are ensured. The obtained results indicate that the automated rainfall generator produces raindrops with Christiansen uniformity coefficients higher than 70%, and with an adequate distribution of raindrop sizes under a range of rainfall intensities between 86.0 and 220.0 mm h⁻¹. The ideal rainfall generator conditions were established for a relatively small area equal to or lower than 1.0 m² and considering rainfall events with return periods of 10 to 100 years.

Soil erosion can cause serious damage to the environment and significant economic losses since uncontrolled erosion processes have detrimental consequences for agriculture and may cause damage to existing civil infrastructure. Geosynthetic products to protect soils against erosion are available, such as geomats, geoblankets and geocells. This paper investigates the performance of geomats and geoblankets for the protection of slopes against erosion caused by intense rainfall by means of laboratory tests using a rainfall simulator. The influence of the presence of vegetation on the slope was also investigated. Two geomats and three geoblankets were tested. The results obtained showed that these products can provide efficient soil protection, but due attention must be paid to some factors such as the product's physical and hydraulic characteristics, good contact with the soil surface, soil cover ratio and endurance under high rainfall intensities. The results also showed that the presence of vegetation is beneficial against soil erosion, but the level of performance improvement brought by the vegetation will depend on geomat and geoblanket characteristics and properties.