Changes on sediment connectivity at seasonal scale in a temperate humid farmland catchment

LÓPEZ-VICENTE MANUEL; ARES, MARÍA GUADALUPE; FAJARDO, LUISA; VARNI, MARCELO; CHAGAS, CELIO

Conferencia; Biohydrology 2019- Biohydrology Today: Humans and Nature; 2019

The spatial pattern and magnitude of runoff (Q) and sediment connectivity (SC) is influenced by topographic factors, rainfall characteristics, soil properties, man-made landscape elements, and land uses. During low-intensity rainfall events (Re), the kinematic dispersion of runoff is dominant, whereas geomorphologic dispersion becomes more dominant for larger intensities. Erosive events (high rainfall depth and/or intensity) activate the entire catchment, whereas some parts do not significantly contribute to runoff during low- and medium-intensity events. In this study, we evaluated the changes on SC in a temperate humid farmland catchment associated with three different rainfall-runoff events (RQe#1: 03/05/2012, 65.2 mm, I30=27.6 mm/h, and 39 h; RQe#2: 09/06/2012, 29.4 mm, I30=8.4 mm/h, and 52 h; and RQe#3: 12/19/2012, 38.6 mm, I30=57.2 mm/h, and 27.5 h). The study area is a headwater sub-catchment (592 ha) of Del Azul stream, located in the Argentine Pampas Region. The SC maps were obtained by running an updated version of Borselli´´s SC index (IC) using the D-Infinity approach, and modifications made on the slope gradient map. All simulations were made at 5 m of cell size, and the map of roads and trails was included as an important factor that influenced the overland flow pattern. Three C-RUSLE factor maps were generated with mean values of 0.06548, 0.11778 and 0.07395 for RQe#1, #2 and #3. Three different stream networks (StN) were mapped using satellite images (Spot 4 and 5), and used as the simulation?s target of each RQe. The total length of the StN was of 4,572, 6,929 and 10,031 m for the RQe#1, RQe#2 and RQe#3. The highest IC appeared during the RQe#2 (-7.277 ± 1.851), followed by the RQe#3 (-7.593 ± 1.784) and #1 (-7.711 ± 1.696). The spatial pattern of SC changed over the events, and the StN and trails mainly explained these patterns.