Big Flood Research Articles

The Kosi Pralaya; Could the Catastrophe have been Averted? And What Next?

The Kosi river breached its eastern embankment at Kushah in Nepal on August 18, 2008 causing havoc and misery to over 50,000 Nepalese and 2.5 million Indians in the state of Bihar. The affected people lost their homes, farmlands and livelihoods. Four months after the disaster, the affected people are still living in plastic tents in winter. Due to the impact of this catastrophe on the more industrialized and prosperous eastern Nepal, the overall effect on the country’s economy has been severe. At the time of the breach, the river was actually below the level of normal discharge. There was no big flood in Kosi. This was not Nature’s wrath but simply human failings. Bihar’s Water Resources Minister, Vijender Yadav, admitted “The breach happened due to lackadaisical maintenance of the embankment’, but laid the blame on the “previous government”. With timely action such a disaster could have been averted. Saif Uddin Soz, India’s Union Minister for Water Resources, has already said publicly that “Kosi is in focus this time in particular … our main interest is flood control and irrigation,” a statement that puts focus on implementation of the Sapta Kosi High Dam in Nepal. This dam will be built at a great social and environmental cost to the Nepalese people due to submergence of limited fertile valleys, displacement of large number of villagers and over 300 km of very large link canals from both banks of the dam (Kosi-Mechi and Kosi-Ghagra Links) to the Indian border. The attraction to Nepal is, of course, the 3,300 MW of power it will make available for export. The Sapta Kosi High Dam needs to wait until the vital 13-year pending issues of the “signed, sealed and done” 6,720 MW Pancheshwar Multipurpose Project on the Mahakali are finalized.Key words: Kosi Catastrophe; Sapta Kosi high dam; Kosi barrage; flood; NepalHydro Nepal: Journal of Water, Energy and Environment Issue No. 4, January, 2009 Page 2-7

Developing a hybrid multi‐model for peak flood forecasting

AbstractThe present study aims to develop a hybrid multi‐model using the soft computing approach. The model is a combination of a fuzzy logic, artificial neural network (ANN) and genetic algorithm (GA). While neural networks are low‐level computational structures that perform well dealing with raw data, fuzzy logic deal with reasoning on a higher level by using linguistic information acquired from domain experts. However, fuzzy systems lack the ability to learn and cannot adjust themselves to a new environment. Moreover, experts occasionally make mistakes and thus some rules used in a system may be false. A network type structure of the present hybrid model is a multi‐layer feed‐forward network, the main part is a fuzzy system based on the first‐order Sugeno fuzzy model with a fuzzification and a defuzzification processes. The consequent parameters are determined by least square method. The back‐propagation is applied to adjust weights of network. Then, the antecedent parameters of the membership function are updated accordingly by the gradient descent method. The GA was applied to select the fuzzy rule. The hybrid multi‐model was used to forecast the flood level at Chiang Mai (under the big flood 2005) and the Koriyama flood (2003) in Japan. The forecasting results are evaluated using standard global goodness of fit statistic, efficient index (EI), the root mean square error (RMSE) and the peak flood error. Moreover, the results are compared to the results of a neuro‐genetic model (NGO) and ANFIS model using the same input and output variables. It was found that the hybrid multi‐model can be used successfully with an efficiency index (EI) more than 0·95 (for Chiang Mai flood up to 12 h ahead forecasting) and more than 0·90 (for Koriyama flood up to 8 h ahead forecasting). In general, all of three models can predict the water level with satisfactory results. However, the hybrid model gave the best flood peak estimation among the three models. Therefore, the use of fuzzy rule base, which is selected by GA in the hybrid multi‐model helps to improve the accuracy of flood peak. Copyright © 2009 John Wiley & Sons, Ltd.

군자 시험배수구역 합류식 하수관거시스템의 일일하수량 및 직접유출량 산정

A localized torrential rainfall and flash floods which are more frequently occurred by extraordinary atmospheric phenomena and rising sea surface temperature require more hydrological data collecting and analysis for small watershed. Urban watershed hydrological data monitoring system is needed because of big flood potential damage and lack of urban watershed hydrological data. Therefore, Urban Flood Disaster Management Research Center operates small experimental catchments(Sinnae1, Gunja, and Children`s Park) observing and analyzing hydrological data(rainfall, stage, and discharge). In this study, the discharge of combined sewage for Gunja experimental drainage is analyzed with weekly data and day of the week data. Through several analyses in analyzing the urban runoff characteristics and managing the urban sewage system, direct runoff is calibrated and verified by the estimated values of rainfall-runoff model(SWMM).

A contribution to improved flood magnitude estimation in base of palaeoflood record and climatic implications – Guadiana River (Iberian Peninsula)

Abstract. The Guadiana River has a significant record of historical floods, but the systematic data record is only 59 years. From layers left by ancient floods we know about we can add new data to the record, and we can estimate maximum discharges of other floods only known by the moment of occurrence and by the damages caused. A hydraulic model has been performed in the area of Pulo de Lobo and calibrated by means of the rating curve of Pulo do Lobo Station. The palaeofloods have been dated by means of 14C y 137Cs. As non-systematic information has been used in order to calculate distribution functions, the quantiles have changed with respect to the same function when using systematic information. The results show a variation in the curves that can be blamed on the human transformations responsible for changing the hydrologic conditions as well as on the latest climate changes. High magnitude floods are related to cold periods, especially at transitional moments of change from cold to warm periods. This tendency has changed from the last medium-high magnitude flood, which took place in a systematic period. Both reasons seem to justify a change in the frequency curves indicating a recent decrease in the return period of big floods over 8000 m3 s−1. The palaeofloods indicate a bigger return period for the same water level discharge thus showing the river basin reference values in its natural condition previous to the transformation of the basin caused by anthropic action.

Reformative multicast routing protocol based on Ad Hoc

Mobile Ad Hoc networks has been widely applied to military field, emergency management, public service and so on. Because it is uncertain on network and communication, a great deal of energy will be consumed with nodes increasing and creating routing each other. The reformative on-demand multicast routing protocol was putted forward by researching the energy consuming of multicast routing protocol in Ad Hoc. It will decrease consumption in a big multicast flooding through studying the relaying group net structure based on map or wormhole. The energy consumption is reduced 30% by creating the two kinds of routing principles: minimization of energy consumption and minimization of maximum nodes energy consumption. The simulation result indicates that the reformative RODMRP is effective to reduce the energy consuming while routing protocol built.

Mitigating Misery: Land Use and Protection of Property Rights Before the Next Big Flood

Mitigating Misery: Land Use and Protection of Property Rights Before the Next Big Flood

ENSO signals in South America: rains and floods in the Paraná River region during colonial times

Several studies show that the El Nino-Southern Oscillation (ENSO) is an important factor in determining interannual rainfall variability in South America. This signal is detected in the region including Northeastern Argentina, Uruguay and part of southern Brazil, in the form of excessive rains and big floods in the regional rivers. To check that this relationship was similar in the past the objectives of this paper were to construct a time series of large floods in the Parana River region from documentary records, during the sixteenth to eighteenth centuries, and to evaluate the relationship between that historical record of extreme floods, the ENSO documentary evidence (Ortlieb, The Documented Historical Record of El Nino Events in Peru: An Update of the Quinn Record (Ortlieb, sixteenth through nineteenth centuries, Diaz and Markgraf, (eds.), El Nino and the southern oscillation. Multiscale variability and global and regional Impacts. Cambridge University Press, pp. 207-295, 2001; Quinn and Neal, The historical record of El Nino events, Bradley and Jones (eds.), Climate since a.d. 1500, Routledges, pp. 623-648, 1992) and the temperature index of the Pacific Ocean (Mann ME et al., Global temperature patterns in past centuries: an interactive presentation, IGBP pages/world data center for paleoclimatology data contribution series #2000-075. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA, 2000). Considering that the period 1904-2000, where 11 out of 16 floods occurred during El Nino events, it can be concluded that the proportion of years with exceptional flow volume in the Parana River in years with El Nino events in the seventeenth and eighteenth centuries was relatively lower than that of the twentieth century. The reason for this difference is discussed.

A DRAG COEFFICIENT OF BODIES IN AERATED FLOW ON STEPPED CHANNELS

During a big flood in recent years, flood waters intruded into the staircase between ground and underground in an urbane area. Aerated flows are formed in the staircase. Drag force acts on bodies or human legs in a high-speed-aerated flow. The authors proposed a method for estimating the velocity and the depth on stepped channels. Flow resistance and total head in stepped channels were clarified under a wide range of angle of slope, step height, and drop height. On the basis of the flow characteristics of aerated flows, the expression for a drag coefficient on bodies in a high-speed-aerated flow can be reasonably presented. Also, the drag coefficient of a model leg is obtained using the previous results.

Planning and management of flood damage control: the South African experience

en

Hydrological forecast of maximal water level in Lepenica river basin and flood control measures

Lepenica river basin territory has became axis of economic and urban development of Sumadija district. However, considering Lepenica River with its tributaries, and their disordered river regime, there is insufficient of water for water supply and irrigation, while on the other hand, this area is suffering big flood and torrent damages (especially Kragujevac basin). The paper presents flood problems in the river basin, maximum water level forecasts, and flood control measures carried out until now. Some of the potential solutions, aiming to achieve the effective flood control, are suggested as well.

RECOGNITION OF FLOOD HAZARD MAP DISTRIBUTED IN REVER BASIN WITH LITTLE FLOOD DAMAGE EXPERIENCE IN RECENT YEARS

A flood hazard map of the Fushino River in Yamaguchi city was distributed for the residents in 2003. Big flood disasters in the Fushino River have not happened in three decades. The disaster awareness of the residents in the river basin might become weaker. It is important to examine an effect of the hazard map distributed for such residents. One of the purposes of this study is that a residents'; recognition of the hazard map of the Fushino River investigated by a questionnaire survey is reported in order to contribute an improvement of a hazard map of other river.This paper discusses an effectiveness of the hazard map in terms of four viewpoints, i.e., a recognition of the hazard map, a contribution of the hazard map to an improvement of the disaster awareness of the residents, an influence of a predicted water depth on an improvement of the disaster awareness and disaster measures of the residents and the most important information in the hazard map.

The east coast Big Flood, 31 January–1 February 1953: a summary of the human disaster

The Big Flood was the worst natural disaster to befall Britain during the twentieth century, and the scale of its human impact was due to the lack of adequate disaster preparedness. The 307 deaths on land were caused by drowning or from the effects of exposure. Two-thirds occurred in four clusters along the shoreline and mainly comprised inhabitants of post-war prefabricated buildings, bungalows and chalets, with the highest mortality among the elderly. The emergency response was spontaneous and community led, with the main search and rescue completed before central government became involved. No individuals or agencies were blamed for the neglected state of the flood defences or the absence of warnings, along with the post-war shortage of adequate housing, which were the main causes of vulnerability. The media played a limited role, and television was in its infancy. Mental health impacts were either self-limiting or failed to be articulated in a society recovering from the Second World War. The major mitigating factors included the empathetic response of people, locally and nationally, as well as the availability of armed forces personnel based in East Anglia, whose actions played a decisive part in the battle against the sea. The major legacies of the Big Flood were a coastal flood forecasting system, a more scientific approach to sea defences and the building of the Thames barrier.

What happened in 1953? The Big Flood in the Netherlands in retrospect

During the weekend of Saturday 31 January to Sunday 1 February 1953, a storm tide raged across the northwest European shelf and flooded the low-lying coastal areas of the countries around the North Sea. The peak high waters occurred during the night and the storm surprised many people in their sleep. The resulting disaster in terms of loss of life and damage to infrastructure was enormous. In the Netherlands, 1836 people fell victim to the flood; in the UK and Belgium, the casualties were 307 and 22, respectively. The large number of fatalities in the Netherlands was related to the fact that much of the affected area is below sea-level.This paper focuses on the case of the Netherlands. It discusses the history of land reclamation, and the fact that living in low-lying areas protected by dykes, often below sea-level, is an accepted fact of life in the Netherlands. The historical approach to dyke maintenance is then outlined, and the state of the dykes in the early twentieth century and after the war is discussed. The characteristics of the storm and the flood are discussed, along with people's experiences of the first hours and days following the flood. The impact of this human stress has often been lasting--many survivors continue to live with daily memories of the flood. Attention is given to the large-scale rescue and relief efforts, the closure of the dykes during the following nine months and the concept of the Delta Plan, designed to prevent such a large-scale disaster ever happening again. Although the 1953 storm was indeed a low probability event leading to very high storm-induced water-levels, and occurred in combination with spring tide, several arguments are presented that explain why this flood turned into a disaster of such a large scale. Equally, the question is raised whether the disaster could have been prevented. The paper concludes by noting the importance of awareness and preparedness in order to prevent a future storm threat of this scale turning into a disaster of the scope of the Big Flood of 1953.

Regrassing flood-damaged pastures

On the night of February 14th 2004 the lower North Island was hit with a storm system, which would cause the biggest flood seen in the region for over 100 years. The hardest hit areas include the Manawatu, Rangitikei, Horowhenua, Wairarapa and Wanganui regions. In the summer after the event, a survey was conducted of the affected areas. Semi-structured interviews of 52 individual farmers focused on their farm operations, the impact of the flood, and their regrassing strategies. The interviews established the state of the pastures postflood including depth and texture of silt deposit; water levels and flow; duration of inundation; and soil surface condition. The regrassing strategies included seedbed preparation, sowing technique, fertilizer use and weed control. Site measurements made were: pasture cover and species content, and that soil profiles revealed rooting depth and silt depth (if not cultivated). General trends that emerged were that the more thoroughly a seedbed was prepared the lower the risk of pasture establishment failure. Nitrogen (N) applications of 75 kg/ha over the intervening period did not have a significant effect but where deep sediment was encountered two or three applications of N was reported to produce feed and start inputting organic matter (OM). The use of a roller drill increased the reliability of establishment and was essential for the establishment of pasture legumes. Double normal seeding rates (30-40 kg/ha) increased the reliability of success where the seed was broadcast. Many farmers that had no sediment reported perennial weed problems including couch, creeping buttercup and a variety of thistles. Small scale surface cultivation was reported to decrease drying time dramatically in extremely wet areas. Keywords: ground cover, pasture cultivars, pasture establishment, seedbed preparation, weeds and pests

Modelling the Effect of the Hydroelectric Pumped Storage Plant on Hydrodynamic Regime of the Kaunas Reservoir In Lithuania

The Kaunas Reservoir was formed during construction of the Kaunas Hydroelectric Plant (Kaunas HP) on the Nemunas River in 1960. Since 1992 it has also been serving as a lower reservoir for the Kruonis Hydroelectric Pumped-Storage Plant (Kruonis HPP), which currently has four generating units with 200 MW of installed capacity each. There are plans to increase the capacity of this power plant by constructing additional four generating units. Operation of the Kruonis HPP is already changing the hydrophysical regime (water levels and flow velocities) of the Kaunas Reservoir and new units can seriously aggravate the situation by inducing bottom erosion. The objective of this study is to determine the optimal number of generating units so that the impact of the Kruonis HPP on the hydrophysical regime of the reservoir would be acceptable. The hydrodynamic model MIKE 21 was used to calculate the flow velocity and water level fluctuation in the Kaunas reservoir for different number of the Kruonis HPP generating units. The Kaunas HP was considered as operating with minimal load or under conditions equivalent to a big flood (2,000 m3/s). The modelling results indicate that the impact of four units is acceptable while simultaneous operation of the eight units at Kruonis HPP would not be desirable.

Part I: Integrated water quality management: river basin approach. Geochemical techniques on contaminated sediments--river basin view.

The big flood in the upper Elbe River catchment area has revealed a wide spectrum of problems with contaminated sediments. So far, an effective strategy for managing contaminated sediments on a river basin scale is still missing and it seems that not much has been learned from the lessons received during the last decade. In the following overview, special emphasis is given to the utilization of geochemically-based techniques for sediment remediation, which can be applied in different parts of a river basin. The examples presented here are mostly from the Elbe River catchment area. In general, new technical problem solutions need a set of practical process knowledge that uses a wide range of simulation techniques, as well as models in different spatial and temporal scales. The evaluation of recent flood events clearly demonstrates the importance of chemical expertise in the decision-making process for the sustainable development in river basins.

CHANGES OF CHANNEL CHARACTERISTICS OF YOSASA-RIVER AFTER DISASTER RESTORATION

Disaster restoration works are commonly preformed based on the technical standard from the reason that there is not sufficient time of investigation and study for emergency construction. Therefore, some rivers that have special characteristics require additional studies on the changes of channel characteristics.In this paper, the result of study of Yosasa-river was described after the disaster restoration works. The channel was considered to have such special characteristics that the natural banks were greatly scoured laterally due to the existence of tight armor coat, during the big flood in 1998 after 60 years. But, the armor coat was found not to be developed by the field investigation, and it was concluded that the degradation was not occurred by the existence of huge amount of sediment transport that was yielded by the bank erosion due to the loose materials of the banks. Now, the channel has protected banks on both sides and the rate of sediment transport is considered to be dramatically decreased. Therefore, additional counter measures are proposed in this case.

Seasonal Changes of Magnetic Susceptibility in Sediments from Lake Zywiec (South Poland)

Lake Zywiec is a man-made lake constructed in 1965 on the Sola River, Beskidy Mountains (South Poland). The lake is the largest one in a flood control reservoir system known as the Sola Cascade. In May and September 1970, separated by a big flood event in July, the lake was sampled for rock magnetic, chemical and granulometric studies. In 85% of the September samples, susceptibility decreases by 10 to 40% compared to the value measured in May. Seasonal changes are also observed in the total Fe content and some heavy metals. A general decrease in Zn, Pb, Cd, Cu and Cr content during the summer season was observed in the whole lake. The content of other metals such as Mn and Ni increased in samples taken in September. The changes observed in the lake sediments could be only an accidental result of the flood or may indeed result from seasonal changes fostered by the flood effect.

Integrated Approach for Environmental Flood Protection for Northern Suburbs of Athens, Greece

In this paper some general design considerations and principles for flood protection and related stormwater design, based on an integrated environmental approach, involving less technical works and preservation of the physical condition of streams and creeks are presented. Sediment control through check dams and the selection of design return period are discussed. The design period should be selected depending on the specific location, the associated design of the receiving stream or water body, and considering the consequences of a bigger flood than the one used for the design. The application of the above mentioned considerations is illustrated in two specific case studies (introductory study for Kifisia and the preliminary study for northern suburbs), carried out by Hydroexygiantiki for areas in the northern suburbs of Athens on behalf of EYDAP, a public company responsible for the water supply and sewage system of the Athens Metropolitan area. The proposed design in each case took into account the special problems and the views of the local authorities in order to ensure that the proposed design is a viable one. Of course it should be always kept in mind that the selected design should be implemented starting from the downstream end and special care should be used in main road crossings.

Flood hazard assessment in Bangladesh using NOAA AVHRR data with geographical information system

Flooded area and flood hazard assessment in Bangladesh were evaluated using remote sensing (RS) data with the geographical information system (GIS). Image data from the National Oceanographic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) were used to analyse Bangladesh's historical flood event of 1988, which sets a hundred-year record for the inundated areas, with severe damage occurring throughout this region. Cloudy skies often occur during big floods, and visible and infrared rays observed by the NOAA AVHRR cannot penetrate cloud cover. We therefore proposed a new algorithm for classifying cloud covered pixels into water or non-water categories. In order to estimate the flooded area accurately, the images taken during the flood and dry season which were classified into water and non-water categories were superimposed. A new flood hazard map, created from the land cover category and elevation height data which were ranked by flood affected frequency, can be used to evaluate flood risk using only RS data and elevation height data. Copyright © 2000 John Wiley & Sons, Ltd.