Analysis of α Parameters: Nakayasu Synthetic Hydrograf and Collins Method in Optimizing the Dimensional Planning of Water Buildings

Acep Hidayat

Acep Hidayat

Keywords: Alpha Parameters, Watershed Area, River Length, Slope, Form Factor

Abstract

The limited availability of hydrograph data is an obstacle to waterworks planning. This obstacle makes synthetic unit hydrograph (HSS) models provide considerable benefits for waterworks planning. Ideally, each watershed has a unit hydrograph with its own unique characteristics.

Observations of hydrograph characteristics in each watershed and all watersheds in South Sulawesi Province have many differences. Modeling is carried out based on the Alpha equation with the influence parameters of the watershed area (A), river length (L), slope of the riverbed (S), form factor (FD), and concentration time (tg).

The data used is the data of the hydrograph observation unit in 2011–2017, which is then calculated with the HSS Nakayasu Method and Collins Method. From the calculation of the HSS Nakayasu and Collins Methods, each peak discharge (QP) is obtained, which has the smallest difference between the two of them. With these results, the α parameter value of 0.60 is obtained. The value of the α parameter obtained is in accordance with the actual river characteristics of the Janeberang watershed, so it can optimize the planning of water building dimensions.

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