<p>Vortex drop shafts are an effective solution for conveying flow in steep elevation drops. This study presents an experimental investigation of a new vortex drop shaft inlet design, the Archimedean spiral inlet with the aim of facilitating construction is introduced. The effects of the inclined channel slope, Archimedean spiral slope, and flow inlet opening angle on the hydraulic performance of this inlet were examined under different flow rates. The results showed that the effective efficiencies related to both discharge capacity and the spiral itself increase on gentle slopes compared to a no-slope condition. However, on steep slopes, the effective efficiency of the spiral decreases due to hydraulic jumps or flow blockage. Therefore, optimal slope configurations can be identified to simultaneously enhance both effective efficiency metrics. Using analysis of variance, nonlinear models were developed to estimate the effective efficiencies. To maximize the response variables, optimization was performed using the utility function. The optimization results showed that with an 8.8% slope of the inclined channel, a 14.8% slope of the Archimedean spiral, and an opening angle of the flow inlet of 240 degrees, the effective efficiency for the discharge capacity and the effective efficiency of the spiral increased by 58.33% and 49.64%, respectively; also, reducing the flow rate increased the effective efficiencies.</p>