Investigative study on the peak discharge upper lesti river catchment area, Malang Regency, East Java Province, Indonesia

The peak discharge of the Lesti River is hydrologic information needed to plan and design the Brantas River's water structures. Hence, this study aims to analyze varied peak discharge among methods and calibrate the calculated to observed peak discharge. The analysis of peak discharge using Nakayasu SUH, Snyder SUH, DPMA-IOH, and Rational method. The result showed varied peak discharge among calculated methods and observed peak discharge. Physical parameters were considered well-identified as optimized parameters that produce varied peak discharge. Estimating peak discharge in the Lesti River catchment needs accurate hydrological input data. Most peak discharge estimation methods require physical characteristics as input. Therefore, the relative error measured that Nakayasu was considered relatively more accurate than others. The accuracy level expressed that Nakayasu SUH was an expected method appropriate to catchment characteristics.