<p>Rainfall induced landslides is one of the major concerns all over the globe. The infiltration of the rainwater reduces shear resistance of the soil mass by reducing matric suction and increases destabilizing force by adding to the self-weight of the soil. To enhance the stability of such slopes, surface and sub surface drains are widely used. The effectiveness of the drainage system depends upon factors such as location of the drain, length of the drain, inclination of the drain, size of the drain, spacing between the drains, design rainfall intensity and hydraulic conductivity of the soil. However, the clear guidelines on the design of the drainage system for slopes in hilly terrain are missing. In the present study, a numerical analysis comprising of seepage analysis and stability analysis is carried out in SEEP/W and SLOPE/W, respectively. The seepage analysis involves finite element simulations whereas the stability analysis involves conventional limit equilibrium calculations. A slope of height 12&#xa0;m with inclination of 30° is considered and factors affecting subsurface drainage design are investigated. The factor of safety against drainage (F_D) increased with decrease in the drainpipe length. However, the factor of safety against stability (FOS) decreased with decrease in the drainpipe length. For the slope considered in the present study, the drainpipe length that satisfies both factor of safety against stability and factor of safety against drainage criteria is found to be 0.49&#xa0;H, where H is the slope height; for design rainfall of 11&#xa0;mm/hr and duration 24&#xa0;h. Further, the drainpipe at the toe is found to be most effective in draining the pore water out. The drainpipes provided in the upper region of the slope are found to be redundant for the design rainfall of intensity of 11&#xa0;mm/hr and duration of 24&#xa0;h. Based on the investigations, guidelines are proposed to design subsurface drainage system which may be adopted by the practicing engineers.</p>