Evaluation of the Effect of Hamao Detention Pond on Excess Runoff from the Abukuma River in 2019 and Simple Remodeling of the Pond to Increase Its Flood Control Function

Due to the recent increase in the intensity of rainstorms, the Japanese government has announced a new policy of flexible flood mitigation measures that presupposes the release of water volumes exceeding the river channel capacity onto floodplains. However, due to the limited amount of quantitative measurement data on excess runoff, it will take time to formulate planning standards for remodeling and newly constructing flood control facilities reasonable enough under current budgetary constraints. In this study, the capacity shortage of a flood detention pond was evaluated against the excess runoff from a severe 2019 flood event by combining the fragmentary measurement data with a numerical flow simulation. Although the numerical model was a rather simple one commonly used for rough estimation of inundation areas in Japan, the results were overall consistent with the observations. Next, in accordance with the new policy, an inexpensive remodeling of the detention basin, which was designed according to conventional standards, was simulated; the upstream side of the surrounding embankment was removed so that excess water flowed up onto the floodplain gradually. Numerical experiments using the simple model indicated that the proposed remodeling increased the effectiveness of flood control remarkably, even for floods greater than the 2019 flood, without much inundation damage to upstream villages.

ENVIRONMENTAL STUDY ON COLLECTING OF RAINWATER HARVESTING AND DETENTION POND DESIGNING TO REDUCE THE LOADS ONTO SANITARY NETWORKS

Rainwaters harvesting has been the vital source of water resource for drinkable and non-drinkable purposes in the ancient eras. As the water transportation systems stayed not used for water supply for these times. At present, the water distribution systems have upgraded, but the request to fresh water is increasing due to the inhabitants growing, and development. The water shortages and presented water supply for drinking are limited, which insisted the specialists working in the water division to search for solutions could be applied to the water deficiency that many countries in the world are facing. Optimization of water habit and the management of water resource will be able to aid to passing water shortage. This work contain the first designing and accumulation of rainwater from the rooftop in Baghdad City. Moreover, designing a detention pond using hydrology studio software programme to store the collected water.

Program Development for Detention Pond Sizing Based on Excel Using SWMM Engine

In this study, we developed a program for detention pond sizing based on Excel in order to improve user convenience. The program includes a function for the derivation of flood hydrograph that was embodied by using the rational method hydrograph for connecting the design of the stormwater pipe. The design method of a permeable detention pond that is a kind of low impact development (LID) technique was also implemented. In addition, the operation of the program was found to be stable, and various discharge structures such as weir, pump, and pipe could be easily conducted using the engine of the stormwater management model (SWMM). The developed detention pond sizing program was applied to the actual design. Subsequently, similar results were derived by comparing with the actual design, and it was found that the program was appropriate.

Relationship Performance of Cylindrical Detention Pond (CDP) as Depression Storage and Runoff Reduction Under Fully Saturated Condition

Permeable pavements are a key Storm water management measure employed both to attenuate surface runoff in urban areas and to filter urban storm water pollutants. Existing permeable pavements (PP) are design with the specific percentage porosity whereby enabling excess rainwater to infiltrate through the system and acting as a depression storage at the same time. Depression storage basically refers to the volume of water trapped in the depression when the precipitation of a storm reaches the ground and filled up all the depression before it can flow over the surface. Cylindrical Detention Pond (CDP) is an alternative paving material that may alleviate many of the hydrological problems caused by urban runoff from developed areas. CDP consist of three basic component; top cover, bottom cover and hollow cylindrical at centre (300 mm thickness). The hollow cylindrical has approximate 50 percent porosity from the total solid of component, which is every 1 inch (25 mm) of pavement depth can hold 0.5 inches (12.5 mm) of rain in theoretical. In this study, the depression storage rate of CDP was investigated under three different rainfall intensity scenarios which are 77 mm/hr (low), 153 mm/hr (medium), and 230 mm/hr (heavy) respectively whereby it function to monitoring the analytical trend line. The experiment was conducted in model box in the laboratory under fully saturated condition. It found that the CDP can performed to detent the water until 180 min of excess rainfall for all 2 year ARI, 5 year ARI, 10 year ARI, 20 year ARI, 50 year ARI and 100 year ARI with different rates. CDP’s able to reduce the runoff up to 77% of the total rainfall volume. The result was proved the hollow cylindrical at centre of CDP very effective in runoff volume reduction according to the different ARI trend line projection.