Floods are one of the most damaging and common forms of natural disasters globally. There are many ways to protect against these effects, including engineered solutions and floodplain restoration. However, human behavior is generally not considered in these solutions, which can lead to unexpected and costly long-term consequences. The paradigm of sociohydrology can prevent such generalizations, since this perspective considers humans as an important aspect that continuously influences, and is likewise influenced by, their local watercourses. When we consider human behavior as acting within, rather than driving, the hydrological system, we can better assess differing scenarios for development and identify complex socioeconomic factors affecting flood risk. By including changes in human behaviors, we can observe both proactive and reactive changes in the system preluding and resulting from theoretical floods and better determine what sorts of measures would likely be most suitable for an area. Hidalgo County, Texas is subject to frequent and severe flooding, particularly in lower-income and nonwhite neighborhoods. Of these, colonias, defined as “residential area[s] along the Texas-Mexico border that may lack some of the most basic living necessities, such as potable water and sewer systems, electricity, paved roads, and safe and sanitary housing,” are among the most impacted due to their lack of infrastructure. The Alberta Drainage Project is the result of years of community efforts to install and expand urban storm water drainage infrastructure to include approximately 1000 residents in six colonias near Alamo, Texas. Although the county and private businesses involved with project construction appear to have completed private studies forecasting the effectiveness of the drainage system, little consideration has been paid to the long-term impacts reduced flooding may have on human behavior and, as a result, flood risk. This study aims to apply a sociohydological perspective to examine flood risk in the colonias within Hidalgo County, Texas, and the potential impacts the Alberta Drainage Project may have on mediating this risk. We will determine these risks by utilizing hydrologic modeling of extreme events paired with systems dynamics methodology. These models will allow us to see the short-term impacts the drainage project will have on flood risk. Additionally, they will allow us to predict how different policy focuses will affect changes in land use patterns in the floodplain and the resulting long-term flood risk. Our study should help guide local leaders in their policy-making decisions during and following the project’s construction to best minimize future costs and maximize future benefits associated with the infrastructure. The potential implications of this study also extend further than one small community. Colonias are in many ways similar to communities in developing countries in that they may lack access to basic necessities, economic resources, and political influence. Enhancing these communities’ standards of living is a primary focus of much international relief programs. By utilizing the framework established in this study, local leaders can better understand what long-term effects such projects may have on effected communities and direct development in ways that continue to sustain these areas far into the future.
Flooding early warning systems are articulated procedures that aim to alert the occurrence of river level increase or a possible flood, to the populations located downstream in risk areas in order to protect their lives. These procedures include monitoring of hydroclimatic conditions (rain and river levels), analysis of this hydroclimatic information, forecast of potential impacts, early dissemination of information to the population and the consequent actions based on a series of protocols that must be established by the appropriate entities.
In El Salvador, the actors responsible for flooding early warning systems are the Ministry of Environment (MARN) through the Department of Environmental Observatory (DOA), the Ministry of Interior through Civil Protection and the communities, in a coordinated work that has been developed and improved since 2002.
The research involved the development of tools that allow MARN the analysis of hydroclimatic information of telemetric stations that send information in real time, effectively and quickly, in order to identify variations that could generate some impact such as the arrive time to the risk zones, so hydrological parameters and hydrological modeling were developed in different basins of the country.
Some of the developed hydrological parameters helped identify different stages for each of which was established a procedure for action: monitoring, warning, and emergency alert. These hydrological parameters are as follows: a) thresholds of river levels; b) precipitation intensity thresholds; c) transit times of the current between hydrometric stations located in the same basin; d) relationship river levels at stations located in the same basin; e) relationship between rainfall amounts and increased river levels; f) isochronous curves that estimate the arrival time of level river increased to areas of potential impact; g) temporal distributions of rain. Hydrological modeling were performed based on models rain runoff, the results of which can set the stage hydrological level is expected in certain situations. These tools have proven to be very effective for early warning systems, because with developed hydrological parameters a quick analysis of recorded information is reached, which allows to take the necessary measures within the system, besides complementing results hydrological modeling, without subordinating the hydrological analysis to modeling results. The development of these tools has been carried out based on statistical and hydrological observation and analysis of historical flood information as well as information recorded by the telemetric stations, linking variables rain, river levels and affectation. These tools are updated as conditions change in land use in the basins, as well as changes in riverbeds situations of erosion or sediment deposition.
Changes in hydrological processes associated with climate change may increase frequency of severe flood and drought events. More effective water resources management is needed to mitigate impacts of those severe water-related disasters. As reservoirs can play an important role in water resources management, sophisticated operation of reservoirs considering real-time hydrological predictions can improve the capacity of existing water resources management systems to deal with severe floods and droughts.
In order to provide reservoir managers with quantitative and science-based information on expected benefits and risks to introduce operational hydrological predictions into reservoir operation from the long-term viewpoint, a Monte Carlo-based method to analyze effectiveness and risks of integrated operation of a multi-purpose reservoir for flood management considering real-time ensemble hydrological predictions is developed in this study. Preliminary release operation, in which water stored in the reservoir is released just before a flood event considering real-time hydrological predictions to secure more empty volume in the reservoir for flood control, is considered as an integrated reservoir operation method in this study. The outline of the proposed method is described as follows. Firstly, a model for synthetic generation of ensemble hydrological predictions with designed error structures is developed. The mean error of ensemble mean predictions and the spread of ensemble predictions are considered as the parameters to represent prediction error structures. A Monte Carlo simulation of preliminary release operation of the target reservoir is then conducted considering a number of ensemble hydrological predictions with a designed error structure generated by use of the model developed in the previous process, in order to analyze the effectiveness of preliminary release operation in flood control as well as expected risks in water utilization due to reducing water level of the reservoir. The effects of preliminary release operation are thoroughly investigated by conducting the Monte Carlo simulations of reservoir operation changing error structures of hydrological predictions considered in the preliminary release operation.
The proposed method was applied to preliminary release operation of the Nagayasuguchi Reservoir in the Naka River basin in Japan, clarifying expected effectiveness of preliminary release operation in flood management as well as potential shortage in water storage recovery and its possibility after a flood event with respect to each parameter setting for error structures of ensemble hydrological predictions. This information can be used for calculation of the rational amount of compensation to be paid to stakeholders who have a right to use water of the reservoir for shortage in water recovery. The results also showed the criteria of prediction accuracy that is needed to conduct preliminary release operation safely while recovering storage water level for water utilization after the flood event with more than a certain probability.
Most West African coastal cities have grown into the economic hotspot of their countries because of the past history of colonialism and their closeness to the ocean. However, the ocean and the associated wetlands also bring some risks. Repeated flooding occurs mainly due to the minimal coping capacities of these countries; leading to huge damage and loss of lives together with associated threats like erosion, epidemic diseases, land subsidence and salt water intrusion in fresh water. With the current rapid urban growth, climate change and sea level rise, flooding will be exacerbated and will become a public issue.
During the past four decades, in the data base of the Centre for Research on the Epidemiology of Disasters, the number of disaster flood events in West Africa, evolved from 4 to 19, 42 and 105. Accordingly the number of fatalities also, evolved from 0 to 252, 586 and 1155 respectively. But during the ongoing decade, from 2010 to 2015, 57 disastrous flood events were already recorded with 1169 fatalities.
To cope with floods, some strategies and policies are implemented at regional, national, community or household level. The present trend of flood frequency and the huge magnitude of the damage induced testify that the measures applicable for managing floods are not adequate and efficient. This paper tries to point out the gaps and the challenges that need to be tackled for a proper flood risk management.
To do this, a case study approach is used. Four coastal cities were selected: Accra, Cotonou, Dakar and Lagos. The data used for the analysis is mainly secondary data.
Flood risk management has roughly two parts: flood risk assessement and flood risk reduction. In general, the simple way of determining flood risk as at now, in West Africa, is by flood prone areas mapping and this done by observation and interview. This method is used by local authorities, particularly after flooding. Damage is estimated roughly after flood event mainly to know the number of affected people and organise the relief services. In West Africa, structural measures are insufficent and even the existing ones are not well maintained. Emphasis is put mainly on non-structural measures especially emergency measures.
Adequate data, assessment tools and methodologies are needed to support the choice of measures. But they do not exist due to lack of fund and skilled personnel. They must be developed. Flood risk must be assessed in a holistic manner taking into account at the same time all possible flood types and all possible scenarios of climate and land use changes and sea level rise. long term planning is necessary. Another path that can help is to learn from other countries and screen the local knowledge. Measures should be selected in a way that they safeguard the environment while minimizing the flood damages.
Funding and political will are needed to support the risk assessment and the implementation of measures. A strong legal framework is necessary but scientific research should precede regulations and laws.
Purpose: Number of extreme rainfall is increasing in Japan and these damages are also become obviously. Even we had huge damages in local areas in 2015 and 2016. Japan has tackled with flood and inundation reduction since ancient times but the potential protection level is decreasing now because of climate change. Quantitative evaluation of adaptation for flooding is requested and cost value is useful for discussion of policy decisions. Numerical flood simulation and some GCMs with scenarios can evaluate adaptation effects. Also spatial information showing vulnerable areas is important for policy making. Therefore the distribution of damage cost was made in this study and we discussed the adaption in spatial and temporal. Methodology: 2D non-uniform flow is modeled to obtain the inundation depth and duration, which are used for calculation of flood damage in each landuse according to the economic manual for flood protection (MLIT, Japan). Extreme rainfall as a distribution map is estimated from GEV distribution function using 30 years data, interpolated observed data into a whole Japan, and input these to the model. 4 GCMs and 3 RCP scenarios provide future rainfall, which is used for downscaling and bias correction. Present flood damage is calculated by the difference between damage of GCM input rainfall and 50 years return period rainfall, which is supposed as average flood protection level in whole Japan. Adaptation effect is evaluated as the damage to flood protection of 70 years return period rainfall, which is 20 years return period protection is higher than current flood protection level. Summary: In the case of current flood protection level, future flood damage costs are much different for each GCM with scenario which has double value on the estimation. Roughly the damage cost will be 2 to 3 times in around 2100 comparing with current situation. In the case of adapted flood protection level by increase of 20 years return period for peak discharge, some of all damage costs by all GCMs will be negative to current damage and the average future damage cost with the adaptation is similar to current damage cost that the shift of damage cost in the future is similar to the investment of 20 years return period protection. Even now, Japanese government is continuing flood control but the rate of damage for the future is higher than the increase of flood control by hardware such as dams, dikes and retention ponds. It would be difficult to raise the level for 20 years flood protection in whole Japan until 2100, therefore, all manner of countermeasures are necessary for flood adaptation such as early warning system, evacuation drills and others.