<![CDATA[The rapid expansion of residential, commercial, and industrial areas along the Johar – Lamaran road segment in Karawang Regency has increased impervious surface coverage and surface runoff, resulting in recurring flooding despite the presence of existing drainage channels. This study aims to evaluate the capacity of the existing drainage channels against the 50-year return period design flood discharge and to formulate an appropriate channel redesign. The design flood discharge was calculated using the Rational Method with rainfall intensity derived from the Generalized Extreme Value (GEV) distribution, while channel capacity was analyzed using the Manning formula. Evaluation of nine channel segments showed that the design discharge (0.518–6.579 m³/s) exceeded the existing capacity (maximum 1.87 m³/s) in all segments, indicating that none of the existing channels can accommodate the design flood. Channel redesign using an economic dimensioning approach produced dimensions sufficient to meet the required capacity, whereas the conditional dimensioning approach resulted in unrealistic channel depths for several segments given actual site conditions. All segments were identified as operating under subcritical flow conditions. This study recommends a comprehensive channel redesign incorporating technical modifications such as tiered or closed channels, along with further study using numerical models such as SWMM or HEC-HMS for broader-scale application.]]>
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