Do badlands (always) control sediment yield? Evidence from a small intermittent catchment

The objective of this paper is to analyse the production and the yield of fine sediment in a small mountain catchment (10 km2), characterised by patches of badlands (25% of the catchment area) and drained by intermittent streams. The study area is located in the Southern Central Pyrenees. The study is performed at multiple temporal scales to further highlight: (i) the effect of pulses in the transfer of water and fine sediment; (ii) the contribution of the sediment production from badlands to the sediment yield of the catchment; and (iii) the role of the drainage network as fine sediment source and sink. Significant correlations between meteorological and flow variables were found; specifically, the strongest positive relations were observed between stream flashiness, the duration of the period in which the stream is dry and the suspended sediment concentration. Results indicated that badlands do not always control the export of sediments. At the annual scale badlands supply around 40% of the total catchment sediment yield. Seasonally sediment produced in badlands can be higher than the amount exported at the catchment outlet, suggesting the channel network acts as a sink. In terms of sediment production, badlands represent around of 53% of the total production taking also into account agricultural fields and forest areas. Results emphasise the key role of the channel network on controlling pulses of sediment transfer, in direct relation to the intermittent character of the streams. The frequency and magnitude of such pulses determines the catchment Sediment Delivery Ratio (SDR), depending on whether the drainage network acts as a sediment sink or source.