Kinds Of Floods Research Articles

Problems and Solutions for the Flood Control Program in Medan City and its Surroundings

Medan City is currently experiencing flooding and this indicates all existing flood control projects implemented over the years have been unsuccessful. Therefore, the main objective of this research is to determine the best solution to overcome floods in the city through a literature study supplemented by a perception survey. The steps implemented include discovering the causes of the flood, determining the failure of the past flood control projects, disclosing the perception of the people affected by floods toward the city government’s commitment, and formulating the best solution to overcome the flood. It was discovered that there are two kinds of floods in Medan city which include the flash/river and the local/residence floods. The flash type was caused by the deforestation in the upstream area of the rivers flowing through the city while the local type is associated with high rainfall, lack of pervious area, and poor urban stormwater management. Moreover, the existing flood mitigation projects were observed to be unsuccessful because they applied the old paradigm with a normalization approach without compensating for the increase in the runoff discharge. This means there is a need to establish naturalization in the upper region of all rivers flowing through the city to reduce river flooding. The maintenance of the existing urban drainage system also needs to be combined with sustainable programs such as storing, absorbing, and reusing strategies to mitigate residence flooding. Furthermore, ten recommendations were proposed to stakeholders to overcome or significantly reduce flooding in Medan City and its surroundings. The first is the alignment of paradigms among stakeholders toward flood management while the last is completing related regulations and law enforcement.

Evaluating the Impacts of Rice-Based Protection Dykes on Floodwater Dynamics in the Vietnamese Mekong Delta Using Geographical Impact Factor (GIF)

This study aims at evaluating the geographical influences of rice-based protection dykes on floodwater regimes along the main rivers, namely the Mekong and the Bassac, in the Vietnamese Mekong Delta (VMD). Specifically, numerous low dykes and high dykes have been constructed particularly in the upper delta’s floodplains to protect the double and triple rice cropping against the annual flooding. For the whole deltaic domain, a 1D-quasi-2D hydrodynamic model setup was used to simulate seventy-two (72) scenarios of dyke construction development in the context of low, medium, and high floods that occurred in the VMD to examine the effects of different flood magnitudes on a certain dyke construction area. Based on the model simulation results, we established an evaluation indicator, the so-called Geographical Impact Factor (GIF), to evaluate the impacts of zone-based dyke compartments on the floodwater regimes along the main rivers for different kinds of floods. Our findings revealed different rates of influences on the floodwater levels along the Mekong and Bassac Rivers under different scenarios of zone-based high-dyke developments. GIF is a useful index for scientists and decision-makers in land use planning, especially in rice intensification, in conjunction with flood management for the VMD and for similar deltas worldwide.

TSD Algorithm to Design CA Based Expert System for Pipelining to Stop Urban Flood

Flood is a frequent disaster disturbing the daily life and sometimes found deadly. Out of all kind of floods, urban flood is avoidable through quick exit of drainage. Urban flood starts water logging that can be eliminated by efficient pipeline structure. A dedicated drainage pipeline structure may facilitate better during urban flood. A Cellular Automata is a theoretical computer science tool used to solve complex problems as well as to design structures. In these days, applications of CA continuously increasing, out of which an application of designing a flood avoidance drainage mechanism using CA based structure presented in this paper. To generate knowledge for an expert system to design a flood free city in initial stage of development of a city this paper presents a structure for maximum way of exit. This structure including tanks connected at every corner to minimize the dependency on ground water and reuse the rainwater. In order to avoid flood, minimum size of tanks has been calculated by proposed Tank Size Descriptor (TSD) algorithm with the help of actual rainfall data. With the help of TSD algorithm any expert system of civil engineering will be able to suggest a design of a flood free city using hexagonal shapes within the cellular automata.

Suitable Low Income Flood Resilient Housing

Climate change is a critical issue for all of humanity. It is predicted that Thailand is likely to have an increasing frequency and intensity of rainfall and storms which, will result in a more severe flash flood problem. Slum residents in Chiang Mai are one of the groups of people who are vulnerable to flooding impacts of climate change. The objective of this study is to analyze the flood-resilient housing style of low-income people. Data from 3 slums (146 households) which encounter different kinds of floods every year, i.e. drainage floods (Ban Sanku: 21 households), river floods (Kampang Ngam: 64 households) and flash floods (Samunkee Pattana: 61 house- holds), were collected. The study found that flood frequency, duration, depth and flow velocity caused damage to the houses, but only flood frequency, duration, and flow velocity were factors affecting the housing structure. If considering only damage to slums which frequently face shallow water depth, slow flow velocity and short duration, all 8 low-income housing styles (A-H) can be built. The high platform house with open space under the house is appropriate for slums located in flooding area where high-level, slow flow velocit y floods occur frequently but for a short duration. It may be a permanent, semi-permanent or temporary structure (D-F). For the other slums facing high flood levels with high flow velocities for a short duration, all permanent housing styles are appropriate. If the objective is not only damage prevention but also living during a flood, per- manent high platform houses with open spaces under the houses are recommended for all slums.

As cheias no sul de Portugal em diferentes tipos de bacias hidrográficas

THE FLOODS IN THE SOUTH OF PORTUGAL IN DIFFERENT KINDS OF DRAINAGEBASINS – The regime of the Portuguese rivers depends on the space and time variation of rainfall. Portugal has clear regional contrasts in the geographical distribution of rainfall. The NW and the Central Mountain Range (Cordilheira Central) are the regions with more rainfall. The NE and the south are the driest regions. Therainfall regime is very irregular. The monthly rainfall regime is clearly Mediterranean with autumn-winter rains (November-March) and an extremely dry summer. The river flows are also very irregular, with severe droughts and surprisingly high flood discharges. These characteristics tend to worsen from NW to SE. The southern rivers have specific discharges 6 to 7 times inferior to the ones of theNW, greater irregularity (the flow in years with more rainfall may surpass 100 to 240 times the flow in driest years), a more severe drought (6 months), almost all are temporary, and flood peaks (200-300 times the average flow) can reach extremely high values.In the twentieth century, floods were responsible for the highest rate of casualties in natural disasters in Portugal, followed by earthquakes: one death for every seven were due to floods. The type of floods known as «progressive floods» mainly affects the big hydrographic basins, such as the River Tagus basin, due to the large flooded area. This kind of flood is caused by heavy rainfall periods connected to the western zonal circulation, which usually lasts several weeks. The dams’ basin system reduces flood frequency, especially in autumn when reservoirs still manage to absorb the highflows after the summer dry period, but cannot «tame» the river. It has even contributed to an increase of the peak flow, as in the 1979 flood. Flashfloods are another kind of floods that occur in Portugal and, unlike the former, are dangerous and deadly, such as those in 1967, 1983 and 1997. They affect the small drainage basins and are caused by heavy and concentrated rainfalls, due to convective depressions (cold pools especially active or depressions caused by the interaction between polar and tropical circulations), namely in the south of the country (Lisbon region, Alentejo and Algarve). In the small drainage basins with a natural regime (uninfluenced by a dam), it is interesting to verify the existence of a trend in these extreme phenomena over the last decades. There has been a clear intensification of flood importance during autumn months, in contrast with an accentuated diminishing in winter and spring months.This trend concerns us mainly for two reasons. Firstly, the rainfall concentration in fewer months lessens its availability in the other months and requires a greater storage capacity. Secondly, this concentration means a bigger rainfall intensity in autumn, with the worsening of the number and intensity of floods and a greater soil loss. Deforestation, soil impermeability, chaotic urbanisation, building on floodplains, the blocking up of small creeks, or their canalisation, the building of walls and transverse embankments along the small creeks courses that work as dikes, contribute to the aggravation of this kind of floods. The floods in rivers of southern Portugal are here analysed, and range from the big drainage basins (River Tagus, 80 100km2), to the smaller ones (Cobres stream, 700 km2; Garganta stream, 1 km2). Also discussed are the human causes that have contributed to increasing the consequences of the floods in small catchments.

Characterization of a Mediterranean flash flood event using rain gauges, radar, GIS and lightning data

Abstract. Flash flood events are very common in Catalonia, generating a high impact on society, including losses in life almost every year. They are produced by the overflowing of ephemeral rivers in narrow and steep basins close to the sea. This kind of floods is associated with convective events producing high rainfall intensities. The aim of the present study is to analyse the 12–14 September 2006 flash flood event within the framework of the characteristics of flood events in the Internal Basins of Catalonia (IBC). To achieve this purpose all flood events occurred between 1996 and 2005 have been analysed. Rainfall and radar data have been introduced into a GIS, and a classification of the events has been done. A distinction of episodes has been made considering the spatial coverage of accumulated rainfall in 24 h, and the degree of the convective precipitation registered. The study case can be considered as a highly convective one, with rainfalls covering all the IBC on the 13th of September. In that day 215.9 mm/24 h were recorded with maximum intensities above 130 mm/h. A complete meteorological study of this event is also presented. In addition, as this is an episode with a high lightning activity it has been chosen to be studied into the framework of the FLASH project. In this way, a comparison between this information and raingauge data has been developed. All with the goal in mind of finding a relation between lightning density, radar echoes and amounts of precipitation. Furthermore, these studies improve our knowledge about thunderstorms systems.

Extreme flash floods in Barcelona County

Abstract. In this paper the catastrophic and extraordinary floods occurring in Barcelona County (Catalonia, NE Spain) are studied, in order to characterise the temporal evolution of extreme flash floods in that area and their main features. These events usually cause economical losses and major problems for undertaking daily activity in Barcelona city. This kind of floods is a very common feature in the North-east of Spain and they are recorded every year in some point of Catalonia. This contribution also shows the frequency of those events, within the framework of all the floods that have occurred in Barcelona since the 14th century, but also describes the flooded area, urban evolution, impacts and the weather conditions for any of most severe events. The evolution of flood occurrence shows the existence of oscillations in the earlier and later modern age periods that can be attributed to climatic variability, evolution of the perception threshold and changes in vulnerability. A great increase of vulnerability can be assumed for the period 1850-1900. The analysis of the time evolution for the Barcelona rainfall series (1854-2000) shows that no trend exists, although, due to the changes in urban planning, flash-floods impact has changed over this time. The number of catastrophic flash floods has diminished, although the extraordinary ones have increased.