Landslide initiation has multiple preconditional, preparatory and triggering factors, including rainfall intensity, slope angle and slope moisture content. Previous literature only considers a singular variable in effecting failure. This study shows trends typical of previous literature whilst considering how an amalgamation of assorted variables collaborate to effect failure. To better understand the influences of these factors, a series of tests were conducted using a flume device, employed in the generation of modelled single soil layer slope failures. Experiments were performed in 3 series, determined by rainfall intensity (40, 70 and 100 mm/h) and within these series, alterations were made between slope angle (45–55°) and initial moisture content (5–12%). Failure times occurred once pore water pressure had peaked at positive values, as well as, moisture content equalised throughout the slope. Variations in failure time occurred when altering slope angle and initial moisture content. Increasing the initial moisture content created faster failures whilst slopes inclined 45° failed faster with the exception of 100 mm/h intensity experiments. Initial failure times were summarised and used to develop an intensity-duration threshold function of I = 80.065D−0.596.