Infiltration well to reduce the impact of land use changes on flood peaks: a case study of Way Kuala Garuntang catchment, Bandar Lampung, Indonesia

Abstract. Significant land use changes due to rapid development, a central issue in Bandar Lampung and high rainfall intensity are the main triggers for frequent flooding. This study was carried out to define design rainfall intensity based on analysis of hourly temporal rainfall pattern for calculating design discharge, predict the impact of land use changes on flood peaks, and predict the impact of infiltration well on flood peak reduction. The results showed that rainfall distribution pattern for storm duration of 4 h are 40, 35, 20 and 5% for the first, second, third and fourth hour, respectively. Analysis on land use changes underlined that if 30% of the catchment area is maintained for green land then flood peaks can be decreased. However, with city development, land conversions are intended for settlements, industries and trading areas which will increase flood peaks significantly. Application of infiltration well in the catchment can reduce surface runoff depends on the density and dimension of the well. The results suggest that using infiltration well with diameters between 0.8 to 1.4 m which are applied each in every 4000 m² of land area will reduce flood peaks from 6.9 to 12.6%. While the application of infiltration well with density of 500 m² will reduce flood peaks from 55.21 to 99.8%. Commitment and relevant government policies and community participation will encourage to undertake flood reduction measures.