Stormwater Management System of the surrounding areas from 2no gate to Kaptai Rastar Matha in Chattogram

The economic metropolis of Bangladesh is Chattogram, the port city. Each year's heavy precipitation results in inundated streets and low-lying regions, making life miserable for city residents. The study focuses primarily on the significant areas encircling 2no Gate to Kaptai Rastar Matha. The Noa Network, which consists primarily of Choshma Khal, Mirza Khal, and Noa Khal, is the principally responsible canal network for these regions and joins the Karnaphuli River. This research examines a methodology for estimating the municipal stormwater runoff from the catchment area. The Digital Elevation Model (DEM) for the study area was processed in ArcGIS 10.5 using terrain preprocessing tools to outline the basin, sub-basin, and stream network. The complete sub-catchment area was divided into six watersheds using ArcGIS 10.5. HEC-HMS was used to extract hydraulic parameters of the river basin based on terrain preprocessing results. These hydraulic parameters were then utilized in HEC-HMS to estimate stormwater discharge. We utilized Bangladesh Meteorological Department (BMD) precipitation intensity data from 1974 to 2022 to accomplish this. With the aid of BMD precipitation data, the current condition of the channel's drainage capability for rainfall runoff is evaluated using the HEC-HMS hydrologic model for return periods of 2,5,10,25,50,100 years. In addition, lag time and time of concentration were calculated. The utmost discharge for a 25-year return period was determined to be 172 cumec, while we designed the canal’s capacity to withstand a flow of approximately 180 cumec. Existing canal capacity should work fine for at least till 10 years return period. But regarding the possible climate change our suggested canal cross section can be adopted. It has been analyzed and identified the causes of urban flooding and proposed solutions to remedy the situation. The proposed cross section may differ in a few points from the CDA masterplan due to the use of various design criteria or routing methods. Numerous distinct values, such as Cure Number (CN) and Manning's n, were utilized as precisely as feasible because they can significantly alter the outcome. Finally, in order to resolve this waterlogging issue, the necessary structural measures must be implemented, but public awareness and effective drainage management are also required.