Variability of Suspended Sediment Runoff as an Expression of the Long-Term Dynamics of Loess Gully Development—An Example from the Lublin Upland (Eastern Poland)

In the 20-year period from 2003 to 2022, water runoff and suspended sediment load in a forested gully system with a total length of 7.5 km was recorded. The branching gully system cuts through an agricultural catchment of 1.24 km2 located within the loess plateau of the Nałęczów Plateau (E Poland). A rain gauge was installed close to the watershed and in the gully mouth water runoff was monitored using a limnigraph, installed with a water gauge on a Thomson triangular weir. To determine suspended sediment concentrations during erosion episodes, water was sampled at a frequency dependent on the rate and duration of the runoff. The aim of the monitoring studies was to specify the relationship between flow rate and suspended concentration for different water runoff conditions, which were used to calculate sediment load. The contribution of propluvial and pronivial runoff to gully development was assessed, particularly in the transport of sediment out of the catchment, and unit denudation rates were calculated as less than 1000 Mg km−2 year−1, average 173 Mg km−2 year−1, and during a single event as a maximal 900 Mg km−2.