Inundation Reduction Research Articles

Comprehensive Performance Assessment for Sponge City Construction: A Case Study

Sponge City Construction (SCC) can effectively solve urban areas’ water problems. Green infrastructure (GI), the core of SCC, exhibits a multifaceted capacity to deliver many co-benefits, while grey infrastructure primarily serves the single function of controlling rainfall runoff. However, existing assessment indicator systems fail to either consider or evaluate comprehensive impacts. In this work, a comprehensive indicator system has been established to assess the co-benefits of five different GI measures. The system includes twelve indicators from four aspects, i.e., disaster reduction, economic, environmental, and social benefits. This newly established assessment system is applied to Jinan as a case study. Six out of twelve indicators are evaluated using the self-developed Flood Risk Analysis Software and empirical equations. The results show that the inundation reduction ratios are 11.02%, 9.32%, and 8.02% under the 24-h design rainfall with a 5-year, 10-year, and 20-year return period, respectively. In addition, the corresponding direct flood loss reduction rates are 13.86%, 4.28%, and 4.09%. That is, as the rainfall return periods increase, the disaster reduction benefits become less pronounced. On the contrary, other benefits, e.g., groundwater recharge volumes, are more obvious. The corresponding groundwater recharge volumes are 2.23 million m3, 2.86 million m3, and 2.87 million m3, respectively. The proposed indicator system can be adopted to assess the performances of the different GI combinations, which provides effective support and reference to decision-makers in SCC at the planning and design stages.

PHYSICAL MODELLING OF SOLITARY WAVE OVERTOPPING IN THE PRESENCE OF A COASTAL DUNE

Oceanic underwater disturbances are associated with submarine landslides, volcano eruptions, or seismic activity occurring below or near the ocean basin, which can produce tsunami, which have a small amplitude in deep water with a very long wavelength, so they generally pass unnoticed offshore (Robke and Vott, 2017). These types of tsunami waves can cause massive damage or failures to coastal structures (Kato et al., 2007). From the field surveys after the 2004 Indian Ocean and 2011 Japanese tsunami, it was revealed that natural coastal features such as dunes, dense vegetation, and a combination of dunes with vegetation, acted as natural buffers and provided protection to infrastructure and communities further landward (Fritz and Borrero, 2006; Wijetunge, 2006; Murthy et al., 2012; Wijetunge, 2012). The role of coastal forests, such as mangrove vegetation, on tsunami run-up and inundation reduction, have been extensively studied by many researchers with physical and numerical modeling (Husrin et al., 2012; Yao et al., 2015; Esteban et al., 2017), but not the influence of coastal dunes in offering direct protection. Hence, the present research aims to investigate the mitigation of tsunami run-up and overtopping by coastal dunes.

Evaluation of irrigation network performance at the anjir serapat lowland irrigation area central kalimantan

The Anjir Serapat lowland Irrigation Area in Central Kalimantan is an agricultural area that supports the Food Estate program. Irrigation water comes from rainwater. The existing irrigation network cannot remove excess water during the rainy season, causing inundation in low-lying areas. Stagnant water causes the pH of the water to drop so that it becomes acidic. Acid inhibits the absorption of nutrients, interfering with rice plants’ growth. This study aims to evaluate the performance of irrigation networks in removing excess rainwater. Performance evaluation was carried out with the help of flow simulation using HEC-RAS. The simulation was carried out with three scenarios, namely scenarios with existing geometric conditions, channel normalization scenarios, and normalization scenarios, along with the addition of sluice gates. The normalization scenario and the addition of the sluice gate were more effective in reducing the area of flooded land by more than 20 cm to 158.71 hectares, with a reduction of 48.27% from the existing scenario. For land with lower contours, where not all inundation can be discharged into the channel, it is necessary to add a pump. Further studies are needed to see the effect of adding pumps on the reduction of inundation in the field.

Deciding on fitness‐for‐purpose‐of models and of natural flood management

AbstractThis article has taken a distributed modelling approach to examine the potential for hillslope storage bunds as a natural flood management (NFM) strategy to mitigate the effects of downstream flooding if deployed extensively in the 209 km2 River Kent catchment in Cumbria (UK). To do so, a novel invalidation approach has been taken to calibrate an ensemble of Dynamic Topmodel parameter sets considered as fit‐for‐purpose for the prediction of flood peaks. Only 67 realizations out of 100 000 survived evaluation at the peaks of ranked flood hydrographs including the notable 2005, 2009 and 2015 events, together with a process constraint on the minimum area contributing saturation overland flow in the largest storm of record. These 67 events were used as the baseline (before intervention results) to simulate the effect of introducing 1549 storage bunds to temporarily retain saturation overland flows in optimal hillslope locations. The analysis is extended to simulating the reduction of inundation and damage estimates by running the ensemble of Dyanmic Topmodel simulations as inputs to the distributed hydraulic model JFlow for the 2015 Storm Desmond event. Even given such a large number of interventions the effects on the flood peaks and damages in this case were relatively small. The results of the study emphasize the large amounts of storage required in any NFM scheme, with individual features large enough that they are not too quickly overwhelmed, in order to have a significant impact on flood hydrographs and consequent flood damages.

Applicability Analysis of Trunk Drainage Sewer System for Reduction of Inundation in Urban Dense Areas

Urban development naturally aggravates flood damage, causing severe damage yearly. Preparation for flood damage is a part of urban planning, but it is not easy to establish clear mitigation measures in densely populated urban areas. This study analyzed the applicability of trunk drainage sewers as an alternative to installing abatement facilities, a typical structural measure for reducing flood damage in dense urban areas. The study areas included three areas in South Korea where flood damage had previously occurred, and the input parameters of the flood analysis model were calibrated based on the measured runoff, followed by testing with inundation traces. The results of three watersheds were qualitatively evaluated using the Lee Sallee Shape Index (LSSI) method. The applicability of the trunk drainage sewer system in the Gunja and Dowon watersheds were “Excellent” and “Good” in the Dorim watershed. The analysis results for each trunk drainage sewer condition indicated that the peak flow reduction was the greatest at 40% and 60% dimensionless upstream area ratio (DUAR) for 1000–5000 m3 and 10,000 m3, respectively. High hydrological applicability under the same rainfall conditions was demonstrated consequent to analyzing the applicability of the installation of a typical reduction facility and trunk drainage sewer.

Simulated Mitigation of Tsunami Disasters in the Coastal Area of Purworejo Regency, Central Java, Indonesia

The coastal area of Purworejo Regency has the potential to be hit by a mega-tsunami disaster because it includes the southern coast of Java Island which is faced with seismic gaps that may produce large earthquakes in the future. This study aims to simulate tsunami disaster mitigation in the coastal area of Purworejo Regency in an effort to raise awareness and increase the community capacity for dealing with potential tsunamis so that the level of loss can be minimized. The tsunami risk analysis is based on the Disaster Crunch model, which is a combination of vulnerability analysis based on the weighted overlay quantitative method and tsunami hazard analysis based on tsunami inundation reduction modeling and cost distance analysis. The planning of the tsunami evacuation route is based on the network analysis method. The tsunami-risk area with a run-up scenario of three meters in the coastal area of Purworejo Regency 126,29 square kilometers or about 72,52% of the total coastal area. There are five tsunami evacuation plan points, with five main tsunami evacuation routes that lead directly to each of these points.

Effect of Kandangan Pump House on Long Storage Diversi Gunungsari in Sememi

The Surabaya City Government has built a box culvert in the Gunungsari Diversi channel for the Sememi segment to Banjar Sugihan and the Kandangan pump house. The purpose of this study is to describe and analyze the operational impact of the Kandangan pump on the Sememi box culvert capacity.
 Therefore, the Surabaya City Government built the Sememi box culvert as a long storage in the primary channel of the Gunungsari diversion in order to reduce inundation as well as function as a road that can overcome congestion in the area. The Surabaya City Government has also built a Kandangan pump house as an outlet rather than a long storage at the Gunungsari version. The reduction of inundation and congestion can increase the wheels of the economy which have a global impact on cities around Surabaya as well as a smoother access road for the people in West Surabaya to the middle of the city.

Analysis of inundation reduction in drainage channels in the coastal area of the City of Palu with environmental insights

Inundations occur and become problems in the City of Palu. Inundations occur due to outdated drainage systems, high levels of sedimentation, rapid urban development and topography that tends to be flat. The offered alternatives are rehabilitation of existing drainage channels, storage pond equipped with an automatic valve door, rainwater harvesting and gully plugs. Rehabilitation is performed by adjusting drainage depth, with consideration of the shallow groundwater in the area. For rainwater harvesting, the capacity of rain barrels varies from 350-1050 litres, and they are equipped with reservoir wells. With combinations of these alternatives, the inundation reduction effectiveness of catchment area (DTA) 1 is 93.5% and 99.6% for DTA2. Comparing the results to gully plugs, the effectiveness of inundation reduction in DTA1 is 81% and in DTA2 is 98.9%. The Budget Plan for rainwater harvesting varies depending on the capacity of rain barrels, ranging from Rp. 1, 492, 505.00 to Rp. 2, 692, 505.00. Gully plugs also vary in costs from Rp. 556, 000.00 to Rp. 808, 000.00, depending on the size of the gully plug. The first alternative is chosen by the combination of drainage rehabilitation, construction of a storage pond equipped with an automatic valve door, and rainwater harvesting. This is because the reduction effectiveness is greater and the rainwater harvesting maintenance is easier.

Analisis Reduksi Genangan Pada Saluran Drainase Di Pesisir Kota Palu Yang Berwawasan Lingkungan (Analysis Of Inundation Reduction In Drainage Channel At Coastal Palu City With Environmental Insight)

When the rainy season arrives inundation occurs in some areas in Palu, the capital city of Central Sulawesi. It’s due to rapid development, outdated drainage systems, high level of sedimentation and the topographic condition. Solutions to overcome the problem are rehabilitating existing drainage, rainwater harvesting, gully plug and temporary storage pond equipped with automatic valve door. Rehabilitation is done by increasing the depth of existing drainage. For rainwater harvesting, the rain barrels capacity varies from 350 - 1050 liters equipped with storage well. By combining the rehabilitation and rainwater harvesting, the effectiveness of inundation reduction in DTA 1 93,5% and in DTA 2 99,6%. For gully plug, each size of gully plug is set to fit the width of channel. The effectiveness of inundation reduction 81% in DTA 1 and 98,9% in DTA 2. The budget plan for rainwater harvesting between Rp. 1.492.505,- to Rp. 2.692.505,- depending on rain barrel capacity. For gully plug between Rp. 556.000,- to Rp. 808.000,- depending on the size of gully plug. Combination of rehabilitation, temporary storage pond equipped with automatic valve door also rainwater harvesting was chosen because the effectiveness of greater reduction and maintenance of rainwater harvesting was much easier

Impact of gate operating modes of sea dikes on hydrodynamic regime and inundated area in Can Gio Bay

ABSTRACT Ho Chi Minh City gets severely inundated by upstream flooding and a combination of rising spring tides and rain, owing to the combined impacts of rapid urbanization and sea level changes. A sea dike to close Can Gio Bay has been proposed to regulate storage and control water levels in the drainage and sewer system of Ho Chi Minh City. However, this proposed sea dike and different gate operating modes could significantly change the hydrodynamic regime in Can Gio Bay. In this study, a two-dimensional hydrodynamic model was developed to assess changes in the hydrodynamic regime after construction of the sea dike, including fluctuations in the inundated areas in Can Gio Bay mangrove forests. The results show that sea dike construction is an effective solution for controlling water levels and reducing inundation, especially considering a sea level rise scenario in the year 2050. Further, the gate operation mode also affects the effectiveness of inundation reduction, which is approximately 10% better than the same sea dike type without gate operation. However, the sea dike was less effective in a sea water level rise scenario in 2100 for all scenarios.

Inundation due to the tide in the context of sea level rise and the role of Can-Gio forest in the reduction of inundation

Lower basin of Sai Gon – Dong Nai river is lowland. It’s inundated at high tide. Using mathematical model method with the integrated 1D2D model, the inundation hazard due to the high tide in this region has been evaluated through the inundated area. The calculation results also showed that in the case when the damping ability of Can Gio forest is disabled high water level at Nha Be and Phu An can be increased about 2 – 3 cm and the effect will be stronger in the future following the sea level rise. In the case the Can Gio forest is diked to create a reservoir with reasonable in- and outflow directions, the high water level at Nha Be and Phu An can be decreased about 10 - 11 cm and the effect will be stronger in the future following the sea level rise. This water level decrease effect almost compensates the water level increase due to the sea level rise and keeps the maximum water level at Phu An not exceed actual one until 2050 regardless the sea level rise.

Experimental Study on Floating Debris Generated by Solitary Waves Running up a Composite Beach

Yao, Y.; Huang, Z., and Lo, E.Y.M., 2018. Experimental Study on Floating Debris Generated by Solitary Waves Running up a Composite Beach. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 851–860. Coconut Creek (Florida), ISSN 0749-0208.Tsunami induced debris-laden flow is a destructive process, since the high speed and energetic tsunami waves could destroy and carry any items they could move. A key limitation in understanding such flows is the lack of quantitative experimental data. A laboratory-based study on a debris-laden flow under tsunami waves, modelled as solitary waves in a 2-D wave flume is reported here with the waves being incident on a composite 3-slope setup. Here, two rows of debris with different separation distances were tested. The debris reduced the maximum inundation with the reduction increased with the additional row of debris. The maximum inundation, maximum and final debris positions were shown to be more sensitive to the incident wave conditions. Ensemble measures and normalized kernel density functions were used to characterize the spread in the maximum and final debris positions. A newly defined dimensionless mass loading is further developed to characterize the inundation reduction. The obtained experimental results should find use in calibration or validation of numerical models and aid in field estimations of tsunami wave conditions via post-event surveys of the inundation and debris extent.

내배수시설 경계 재설정에 따른 내수침수 저감효과 분석

In this study, we effectively reduce the flood damage through a revise the border for district unit urban drainage system and propose a design technique over the configuration of the sewer network. It was selected in adjacent urban drainage system, analysis the results for the revise of the watershed boundary and inundation reduction effect. The main nodes were chosen to generate a flood damage, the flood mitigation effect was verified. It proposed a emphasis point for revise the border for urban drainage system.

Development of Urban Inundation Reduction Model by Data-driven Estimation and Hydraulic Analysis

This study presents that a development of the data-driven model for the real-time operation of drainage pump station and integrated unban flood inundation model with one-dimensional (1D) sewer system model and two-dimensional (2D) overland flow model that are improved the problems of the existing hydrology and hydrological model. The developed model was applied to Mapo drainage district to confirm adaptability for storm event of September 21, 2010.

Fluent 모형을 이용한 대심도 배수터널 유입부의 통수능력 분석

최근 도심지역의 내수침수로 인한 침수피해를 저감시킬 수 있는 방안으로 대심도 배수터널의 설계 및 시공을 실시하고 있으나, 국내도시유역의 특성을 반영한 설계 및 시공기술에 관한 연구가 부족하다. 특히 유입유량의 흐름형상과 배제효율을 결정하는 낙차공의 중요 구조인 유입부에 대한 연구결과가 미흡한 실정이다. 그러므로 유입부의 형태 변화에 따른 흐름특성 및 통수능력의 분석 연구가 필요하다. 본 연구에서 3차원 수치모형인 Fluent 6.3 모형을 이용하여 대심도 배수터널 유입부 형태 변화에 따른 흐름특성을 비교 및 분석하였다. 또한 실험결과와 수치모의 결과를 비교 및 분석하여 유입부의 흐름특성 분석에 Fluent 6.3 모형의 적용성을 확인하였다. 유입부의 형태 변화(소용돌이형, 나선식, 접선식) 및 유입구의 경사 증가에 따른 흐름특성 분석 결과 유량배제효율은 접선식 유입부와 나선식 유입부가 거의 비슷하게 모의되었으나, 접선식 유입부가 나선식 유입부 보다 유입구의 경사 변화에 관계없이 안정적인 유입부의 통수능력을 나타내고 있다. 그러므로 국내 도시유역의 협소한 지하공간을 고려한 대심도 배수터널 유입부로는 접선식 유입부가 적합하다고 판단된다. Recently, the deep underground storm water tunnel for inundation reduction has been designed and constructed in urban areas. However, practical studies considering characteristics of domestic urban areas are insufficient. Especially, flow pattern and drainage capacity of intake structures are influenced by intake types of a drop shaft. Therefore, it is necessary to analyse flow characteristics and discharge capacity of the intake structure with change of intake types. The computational fluid dynamics (CFD) model, Fluent 6.3, was applied to investigate the flow characteristics of the drop shaft structure for various of intake types (scroll, spiral, and tangential). The Fluent model was carefully assessed by comparing simulated results with the experiment, and there was good agreement between them. The numerical simulation was carried out according to change in intake types and inlet slopes. The simulated results were showed that spiral and tangential-inlet were stably drained the rate of inflow into the drop shaft. However, the tangential-inlet was showed steady discharge capacity at intake regardless of variation of inlet slopes compared with the spiral-inlet. Therefore, the tangential-inlet was appropriate as inlet of the deep underground storm water tunnel that be able to install on narrowish underground space of urban areas.

침수피해 저감을 위한 지하저류조 설치에 관한 연구

도시지역에서의 내수침수에 의한 침수피해는 우수에 대한 배수시설물의 시설용량 부족, 대상지구내 저류지, 유수지 및 조정지의 부족, 배수펌프장 용량부족 등에 의한 범람으로 야기된다. 침수면적은 일반적으로 소규모이지만 도시지역의 경우 자산밀집도가 높아 단위면적당 피해밀도가 높다. 따라서 집중호우에 따른 내수배제의 불량을 고려한 침수구역의 정확한 추정이 필요하며, 이를 통하여 대비책을 강구하는 것이 중요하다. 본 연구에서는 대구광역시 서구 비산7동 지역을 배수구역으로 선정하여 집중호우발생시 유출특성을 모의하고, 침수피해를 저감시키기 위한 방안으로 지하저류조의 설치에 따른 침수피해 저감효과에 대한 분석을 실시하였다. 국지적인 돌발홍수 및 이상호우에 대한 기존 시설물의 배제능력을 검토하고 지하저류조의 설치에 따른 침수피해 저감효과를 분석하기 위하여 10년, 20년, 50년 및 100년 빈도의 확률강우에 대한 유출해석을 실시하였고, 유출해석을 통하여 계산된 월류량에 대한 2차원 침수해석을 실시하여 최대 침수심 및 최대 침수면적을 계산하였다. 본 연구에서는 최대 월류량이 발생하였던 100년 빈도, 지속시간 180분의 확률강우에 대하여 지하저류조 설치에 따른 유출해석을 수행하여 월류량 발생을 저감시킬 수 있는 최적의 지하저류조 위치 및 규모를 분석하였다. The flood damage in urban area has been caused by lack of capacity of drainage facility, insufficient water retention, reservoir & regulation pond, and lack of capacity for drainage pump station etc. In general, inundation area used to be in small scale but in case of urban area, due to high density of assets, it has been experiencing high density of damage in terms of per unit area. Thus it is necessary to have accurate estimation of inundation area by taking into account poor drainage system in connection with heavy rainfall. In this study, runoff simulation during heavy rainfall was carried out in the area of Bisan drainage basin and the effect of reduction of inundation by the installation of underground storage facilities was analyzed as a method to reduce the damage of inundation. To examine existing drainage capacity in time of flash flood as well as abnormal heavy rainfall and to analyze mitigation effect of inundation damage upon installation of underground storage facilities, the rainfall runoff analysis was carried out on the probable rainfall of 10, 20, 50 and 100 year frequency which exceed facility design frequency.

TSUNAMI HAZARDS: FLOW RESISTANCE AND IMPACT MITIGATION BY COASTAL GREEN BELTS

In the aftermath of the Indian Ocean Tsunami, the protection offered by coastal vegetation became evident in many countries affected and the role of coastal green belts in mitigating tsunami impacts has now been clearly recognized. Coastal green belts also attract attention as an environmental friendly and cost effective measure of impact mitigation. In this research, attention was concentrated on expanding the preliminary experimental on the resistance offered by coastal vegetation to tsunami overland flow, to determine the energy dissipation characteristics in detail, and to assess the effectiveness of coastal green belts in tsunami impact mitigation. Detailed experimental studies were conducted in which the vegetation was represented by geometrically similar small scale models. The effectiveness of coastal green belts was assessed by the percentage energy reduction for various forms of vegetation. Reduction levels in the range up to 30 % were obtained in the experiments indicating the possibility of achieving significant levels of energy reduction of tsunami inundation by coastal green belts. The reliance of the level of inundation reduction on the level of energy dissipation was also investigated.

東北地方太平洋沖地震時における防波堤による浸水低減効果検討

東北地方太平洋沖地震時における防波堤による浸水低減効果検討

Coastal Flooding and Protection from Bio-Shields

In addition to the flooding associated with heavy rainfall, coastal flooding can also be caused by storm surges, tidal waves and tsunamis. The potential of such hazards to cause severe damages in coastal regions and the protection offered by bio shields—coral reefs, coastal sand dunes and vegetation was evident in the aftermath of the Indian Ocean Tsunami in 2004. In this investigation, attention was focussed on the mitigation of tsunami induced flooding by coastal vegetation and results of small scale physical model studies carried out to assess the energy dissipation characteristics of selected forms of vegetation and the reduction in the extent of inundation due to the presence of vegetation are presented. The results indicate significant levels of energy dissipation and reduction in the extent of inundation. A vegetation may be characterized by the type of plants, density (spacing), extent, pattern and location and the relative influence of these characteristics on energy dissipation and reduction of inundation are also presented.