Flood inundation processes in urban areas are primarily affected by artificial factors such as drainage facilities, local al-terations of topography and land uses. The objective of this study is to examine the capability of hydrological model SI-MODAS to estimate runoff and investigating the utilization of storage well in controlling runoff in a residential area. The result of the estimated runoff from the hydrological model was compared with the existing capacity of the drainage channel to identify which channel experienced the problem of inundation. The location of inundation was used to determine the location and number of storage well. The results showed that SIMODAS model could be applied in runoff analyses with 8.09% of relative error compared with runoff depth from field measurement. The existing capacity of the channel could not accommodate runoff Q10yr where the inundation discharge was approximately 0.24 m3·s–1 (at outlet point 1) and 0.12 m3·s–1 (at outlet point 2). The inundation problem was overcome by using a combination system between channel normalization (reduce 35% of total inundation discharge) and storage well system (reduce 65% of total inundation discharge). The storage well was designed at 20 locations (at outlet point 1) and 16 locations (at outlet point 2) which each well had a discharge of 0.0058 m3·s–1. The storage well combined with channel normalization could be used as an alternative way to solve inunda-tion problems in a residential area considering the constraint of land space limitation in the urban area.

A flood occurs for many reasons, such as excessive rainfall, runoff coefficient, or an insufficient river channel capacity. The discharge flowing through the floodway depends on the maximum main river dimension that can be normalized. LU/LC changes are affected by runoff discharge, and runoff discharge is affected by the floodway design. The study dis-cusses the effect of land use (LU) or land cover (LC) changes and the design of floodway channel dimensions in the Kali Kemuning watershed, East Java Province, Indonesia. The Nakayasu synthetic unit hydrograph has been used to analyse the runoff discharge, and the Hydrologic Engineering Center’s River Analysis System software analysed the hydraulic proper-ties of river and floodway channels. Results show that the floodway channel design is determined by LU/LC conditions, and the river channel is normalized toward its maximum dimensions. Normalized channel depths and widths vary from 4 to 7 m and 16 to 46 m, respectively. The floodway channel is rectangular, with a bottom width of 10 m and depth of 4.5 m. With the runoff coefficient equal to 0.75, these normalized channel and floodway dimensions are suitable for the flood up to the 100-year return period runoff discharge.