A year-long study in the Bay of Banyuls-sur-Mer (France) assessed the inputsfrom the local intermittent Baillaury River and the stimulationof nearshore phytoplankton blooms.During flash-floods, dissolved inorganic nitrogen, phosphateand dissolved organic carbon concentrations in the river were neither correlated to the river discharge nor to the season.Silicate was correlated to the river discharge.The particulate organic matter load was diluted in a mineral matrix (3–4%)but had a high nutritional quality at the beginning of the flash-flood. The offshore response to the single major flow event (October 2005) was monitored dailyduring two weeks at 350 m (8 m water depth) and 1.4 km from the river mouth (long-term monitoring station, 27 m water depth).The flash-flood signal was partly hidden at the shallowest site by swell resuspension of bottom sediments. At the deepest station, three phases were identified: (1) at the beginning of flow, river dissolved inputs dilute conservatively leading to increased dissolved inorganic nitrogen and silicate concentrations and decreased seawater salinity, (2) during the main turbid pulse, phosphateis released and (3) after the water column cleared,diatom photosynthesis occurred at 3 m below the water surface, leading seven days after the flow peak discharge to a high of 2 µgL−1 of chlorophyll a, which vanished three days later.The nutrients and salinity recovered their pre-flow values at that time.This dynamics of nutrients and chlorophyll during a flash-flood event is consistent with long-term monitoring data.

On 17 July 1983 heavy rainfall resulted in a flash-flood in the headwaters of the West Grain, a small stream tributary to the River Wear in the northern Pennines. Associated with the flood was a series of three boulder-lobes. The morphology of these lobes and the associated sediment facies are described and used to estimate the hydro-dynamic mode of transport and deposition. Estimates of the shear-strength and viscosity are consistent with the initial conclusion (based on the sedimentology) that the deposits represent low-viscosity debris-flows. The boulder snouts moved as inertial grain-flows with an associated pebbly-core exhibiting a degree of matrix strength imparted by intergranular friction. A degree of reworking of the upper surface of the core by fluidal flow during core motion and immediately upon deposition was also identified. The full sedimentary sequence therefore represents debris-flow core deposits subject to low dispersive pressure evolving into fluidal debris-torrent deposits.