Assessing the Effects of Urbanization on Flood Events with Urban Agglomeration Polders Type of Flood Control Pattern Using the HEC-HMS Model in the Qinhuai River Basin, China

Abstract

Abstract:Urban agglomeration polders type of flood control pattern (UAPFCP) is an extensively used pattern for urban flood control in plain water system areas. Urbanization and polders are two main factors that affect the runoff process in these regions. The Qinhuai River basin, one of the representative watersheds of this flood control pattern in East China, was selected to perform the study. Five urbanization scenarios (the historical, current, and three assumed future urbanization scenarios) of the basin were defined in this paper. The Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS) was used to simulate basin runoff. The results indicate that the UAPFCP increased the flood volume (Q v ) and peak flow (Q p ) compared to the results under the condition without polders. With the constant improvement of the urbanization level of the basin, Q v and Q p under the with polder condition increased correspondingly, and the potential changes show a linear relationship. The urbanization and urban agglomeration polders have interactions with flood events. The effect of urbanization on the flood process is weakened because of the existence of urban agglomeration polders. With the constant improvement of the urbanization level, the effect on the flood process caused by urban agglomeration polders becomes gradually weaker.

The Role of the Spatial Distribution of Radar Rainfall on Hydrological Modeling for an Urbanized River Basin in Japan

“…Control specifications are designed to control the time interval of the simulation of any event. The details of the model structures are given in the technical reference manual [37] and the user's manual [39] of the HEC-HMS, which has been used for a variety of analysis and engineering studies due to its flexibility and applicability in other regions to simulate rainfall-runoff processes [5,[17][18][19][20]22,23,[40][41][42][43][44][45][46]. The model looks applicable for predicting hydrological responses using radar rainfall during extreme storm events over Japanese river basins [19,20].…”

“…We used 10-m digital elevation model data downloaded from the website of the Geological Survey Institute. Different methods have been applied to calculate runoff volume, surface runoff, and base flow in the simulations in previous studies [5,[17][18][19][20][40][41][42][43][44][45][46]. Each method has its advantages and disadvantages.…”

“…The Muskingum-Cunge standard method was used to simulate flow in open channels, and the exponential recession method was selected for modeling base flow. The mathematical explanations for each method have been described in previous studies [5,[17][18][19][20]37,38,[40][41][42][43][44][45][46], and the processes followed are described in the HEC-HMS quick guide [39]. Therefore, because we selected various methods for use in each part of the model set-up for the basin, we had to set the initial conditions of the key parameters for each method before conducting the simulations.…”

“…ID is the flow at the start of the storm; RC is basically describing the rate of baseflow decay; and RP is the rate at which the baseflow recedes between storm events. RP and RC can vary based on the condition of the land use and soil type [45]. We collected discharge data at the outlet of each sub-basin for each selected event and selected the average of the ID before starting the rain modeling.…”

“…High-resolution land-use data show that the basin is mainly dominated by urban areas, but includes forests, bare land, and small areas of paddy fields (Figure 4). These land-use and soil-type datasets are generated from different sources and have been used in the HEC-HMS m odel in many studies [5,17,[18][19][20][40][41][42][43][44][45][46]. The two datasets were considered in the creation of the SCS CN at each grid of the selected basin.…”