Flood information systems: Needs and improvements in Eastern India

Flood warning systems offer a large potential for reducing human losses and property damage in flood-prone regions. This article illustrates why official organized systems should not be relied on completely in either developing or developed societies. It then discusses an indigenous flood warning system in a rural area of Eastern India, its value, and its importance in providing an alternative means of detecting, interpreting, and relaying flood warning information to the ultimate users of this information, i.e., those populations most at risk from floods.The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research and is sponsored by the National Science Foundation.     

Environmental change of coastal Sundarbans: Impact on livelihood and standard of living status of indigenous people

There is overwhelming scientific consensus that environmental change is currently having ecological and socioeconomical impacts at the micro and macrolevel. Over the coming decades, the impact of development, climate change, and urbanization on the ecosystem is likely to become even more ruthless in the Sundarbans. Like many other ecologically sensitive areas, the Sundarbans of the Indian state of West Bengal and of Bangladesh are being stressed climatically to the extreme due to their geographical location. This study explores both the ways in which residents of communities in the West Bengal and Bangladesh Sundarbans perceive changes in the environment, as well as intergenerational changes in livelihoods to be driven in a large part by environmental changes. Persons from a total of 368 households were interviewed using a structured interview tool. As an example of differences in perception between residents of the two areas, survey respondents from communities of the Sundarbans of Bangladesh were more likely to perceive that rainfall amounts are changing than did the residents interviewed from the Sundarbans of West Bengal. From the sample data, it is shown that in the Sundarbans of Bangladesh, 59% of the respondents, as compared to 63% of the respondents in West Bengal, reported that they had chosen to enter their parents’ occupations. From the multivariate logistic regression analysis, it was observed that, especially in Bangladesh when compared to West Bengal, the state of the environment plays a vital role in whether respondents adopt occupations other than those of their parents.     

Assessing options for the development of surface water flood warning in England and Wales

This paper explores the technical options for warning of surface water flooding in England and Wales and presents the results of an Environment Agency funded project. Following the extensive surface water flooding experienced in summer 2007 a rainfall threshold-based Extreme Rainfall Alert (ERA) was piloted by the Met Office and Environment Agency providing initial steps towards the establishment of a warning for some types of surface water flooding. The findings of this paper are based primarily on feedback on technical options from a range of professionals involved in flood forecasting and warning and flood risk management, about the current alerts and about the potential options for developing a more targeted surface water flood warning service. Providing surface water flooding warnings presents a set of technical, forecasting and warning challenges related to the rapid onset of flooding, the localised nature of the flooding, and the linking of rainfall and flood forecasts to flood likelihood and impact on the ground. Some examples of rainfall alerting and surface water flood warning services from other countries are evaluated, as well as a small number of recently implemented local services in England and Wales. Various potential options for implementation of a service are then explored and assessed. The paper concludes that development of a surface water flood warning service for England and Wales is feasible and is likely to be useful to emergency responders and operational agencies, although developing such a service for the pluvial components of this type of flooding is likely to be feasible sooner than for other components of surface water flooding such as that caused by sewers. A targeted surface water flood warning service could be developed for professional emergency responders in the first instance rather than for the public for whom such a service without further operational testing and piloting would be premature.     

Status report on flood warning systems in the United States

One of the major changes in flash-flood mitigation in the past decade is the number of communities that have implemented warning systems. The authors conducted a survey of 18 early-warning systems in the United States developed by communities or regions to provide protection against flash floods or dam failures. Problems revealed by the study included the following: equipment malfunctions, inadequate maintenance funding, inconsistent levels of protection and expenditure, inconsistent levels of expectations and formalization, varying levels of local commitment to the systems, underemphasis on response capability, and a tendency to over-rely on warning systems. The study also revealed some unanticipated benefits experienced by the survey communities: the warning systems serve as valuable data collection tools, a great deal of interagency cooperation has been demonstrated, and warning systems offer increased alternatives to structural modification projects. The interjurisdictional nature of drainage basins, the evolving roles of the various federal agencies involved in flood mitigation, and the lack of governmental standards of operations for flood warning systems are issues that must be considered as communities make decisions regarding the adoption of warning systems. The record on these systems is too short for a precise assessment of how successful they are; however, results of the study indicate that if the goal of reducing loss of life and property from flooding is to be achieved, warning systems must be only one part of a comprehensive flood loss reduction program.     

PERFORMANCE TRADEOFF CHARACTERISTIC OF A FLOOD WARNING SYSTEM1

ABSTRACT: The performance of a flood warning system can be characterized statistically by three variables: the expected number of detections per year, ND; the expected number of false warnings per year, NP; and the expected lead time of a warning, LT. The Performance Tradeoff Characteristic (PTC) of a warning system is a set of all combinations (ND, NP, and LT) that are feasible to attain in a given system. The concept of PTC is an evolution of the concept of ROC (Relative Operating Characteristic) widely used in detection theory. Each characteristic, ROC and PTC, can be displayed graphically in the form of a family of curves. The displays offer an aid to engineering planning and design of flood warning systems. (KEY TERMS: flood forecasts; flood warnings; reliability; detection; Relative Operating Characteristic; Performance Tradeoff Characteristic.)     

Water quality of the River Ganga (The Ganges) and some of its physico-chemical properties

Summary The water qualities of the River Ganga (The Ganges) over a short stretch from Swarupganj to Barrackpore (in West Bengal) have been determined and are compared with the values reported by the National Environmental Engineering Research Institute of India for the periods 1972–74 and 1979–80. The water quality is generally bad, but not at such alarming levels as previously determined by other agencies. Biochemical and chemical oxygen demand (BOD and COD) levels are high but within tolerable limits. Dissolved oxygen (DO) levels are are fairly high, indicating a reasonable self-purifying capability for the River Ganga. However, nutrient loads containing N and P have increased enormously in recent years.     

Impacts of Human Behavioral Heterogeneity on the Benefits of Probabilistic Flood Warnings: An Agent‐Based Modeling Framework

Flood forecasts and warnings are intended to reduce flood‐related property damages and loss of human life. Considerable research has improved flood forecasting accuracy (e.g., more accurate prediction of the occurrence of flood events) and lead time. However, the delivery of improved forecast information alone is not necessarily sufficient to reduce flood damage and loss of life, as people have varying responses and reactions to flood warnings. This study develops an agent‐based modeling framework that evaluates the impacts of heterogeneity in human behaviors (i.e., variation in behaviors in response to flood warnings), as well as residential density, on the benefits of flood warnings. The framework is coupled with a traffic model to simulate evacuation processes within a road network under various flood warning scenarios. The results show the marginal benefit associated with providing better flood warnings is significantly constrained if people behave in a more risk‐tolerant manner, especially in high‐density residential areas. The results also show significant impacts of human behavioral heterogeneity on the benefits of flood warnings, and thus stress the importance of considering human behavioral heterogeneity in simulating flood warning‐response systems. Further study is suggested to more accurately model human responses and behavioral heterogeneity, as well as to include more attributes of residential areas to estimate and improve the benefits of flood warnings.     

Conceptual Framework for the National Flood Interoperability Experiment

The National Flood Interoperability Experiment is a research collaboration among academia, National Oceanic and Atmospheric Administration National Weather Service, and government and commercial partners to advance the application of the National Water Model for flood forecasting. In preparation for a Summer Institute at the National Water Center in June‐July 2015, a demonstration version of a near real‐time, high spatial resolution flood forecasting model was developed for the continental United States. The river and stream network was divided into 2.7 million reaches using the National Hydrography Dataset Plus geospatial dataset and it was demonstrated that the runoff into these stream reaches and the discharge within them could be computed in 10 min at the Texas Advanced Computing Center. This study presents a conceptual framework to connect information from high‐resolution flood forecasting with real‐time observations and flood inundation mapping and planning for local flood emergency response.     

AN EMPIRICAL MODEL OF FATALITIES AND INJURIES DUE TO FLOODS IN JAPAN1

ABSTRACT: This paper provides a framework for analyzing flood fatalities and injuries, and it describes the derivation of a generalized flood risk (i.e., flood consequences and their probabilities) function by introducing an integrated index (the number of residential buildings affected by a flood) that represents the major change in the power relation among the flood intensity, regional vulnerability, and resilience. Both the probabilities and the numbers of fatalities and injuries clearly increase significantly after the flood severity (in terms of the number of inundated buildings) passes a branch point. Below the branch point, it is still possible for fatalities and injuries to occur because of the variability in the data and the uncertainty in the predicted fatality values. The empirical models of fatalities and injuries due to floods in Japan suggested the usefulness in predicting fatalities and injuries and evaluating the efficacy of the warning or other emergency response measures.     

ASSESSING THE ACCURACY OF PALEOHYDROLOGIC INDICATORS,HARPERS FERRY,WEST VIRGINIA1

ABSTRACT: Gaging stations established in 1895 at Millville, West Virginia and in 1882 at Harpers Ferry, West Virginia record flows ranging from a maximum of 6,509 m³s^-1 to a minimum of 2 m³s^-1. Historical and botanical indicators were used to extend the systematic flood record of the Shenandoah River for a study reach approximately 7.5-km long. The long systematic record at the site provides a good opportunity to assess the accuracy of these sources of paleoflood information. Habitation of the area by settlers of European descent began in 1733, and historical flood records extend from 1748. Qualitative historical records from different sources were compared to yield the most complete flood history. The correlation between the various sources was extremely high. Botanical flood evidence preserved as adventitious sprouts, tree scars, and ring anomalies were documented in 37 trees. A flood chronology established from these data extended from 1896 to 1955. Botanical indicators provided an accurate, although incomplete, flood chronology. The ability to determine accurate flood stages from paleohydrologic indicators varied. Historical data yielded relatively accurate stages to within 1–2 m; only minimum values of flood stage could be obtained from botanical indicators. These results illustrate some of the strengths and weaknesses of paleohydrologic investigations in the eastern United States.     

Assessing Effectiveness of National Flood Policy Through Spatiotemporal Monitoring of Socioeconomic Exposure1

Abstract: After a century of evolving flood policies, there has been a steady increase in flood losses, which has partly been driven by development in flood prone areas. National flood policy was revised in 1994 to focus on limiting and reducing the amount of development inside the 100‐year floodplain, with the goal of decreasing flood losses, which can be measured and quantified in terms of population and property value inside the 100‐year floodplain. Monitoring changes in these measurable indicators can inform where and how effective national floodplain management strategies have been. National flood policies are restricted to the spatial extent of the 100‐year floodplain, thus there are no development regulations to protect against flooding adjacent to this boundary. No consistent monitoring has been undertaken to examine the effect of flood policy on development immediately outside the 100‐year floodplain. We developed a standardized methodology, which leveraged national data to quantify changes in population and building tax value (exposure). We applied this approach to counties in North Carolina to assess (1) temporal changes, before and after the 1994 policy and (2) spatial changes, inside and adjacent to the 100‐year floodplain. Temporal results indicate the Piedmont and Mountain Region had limited success at reducing exposure within the 100‐year floodplain, while the Coastal Plain successfully reduced exposure. Spatially, there was a significant increase in exposure immediately outside the 100‐year floodplain throughout North Carolina. The lack of consistent monitoring has resulted in the continuation of this unintended consequence, which could be a significant driver of increased flood losses as any flood even slightly higher than the 100‐year floodplain will have a disproportionately large impact since development is outside the legal boundary of national flood policy.     

DEVELOPMENT OF EARTH SATELLITE TECHNOLOGY FOR THE TELEMETRY OF HYDROLOGIC DATA1

ABSTRACT The use of satellite telemetry is playing a major role in the collection of hydrologic data. Advancing technology and availability of government satellites have permitted many agencies to take advantage of new procedures for acquiring data from automated remote data collection stations. Experiments with Earth satellite technology started in the 1960's and 1970's, with the polar-orbiting National Aeronautics and Space Administration Nimbus and Landsat satellites. Subsequent advancements took place through the development phase to operational systems using the Geostationary Operational Environmental Satellite (GOES) of the National Oceanic and Atmospheric Administration. This satellite system supports more than 2,500 active telemetry sites, of which approximately 1,200 are Geological Survey stream-gaging stations for the collection of hydrologic data. A satellite data collection system is made up of three primary components; a small battery-operated radio, and Earth-orbiting satellite, and an Earth receive and data processing station. The data relay satellites' vast aerial view of the Earth's surface gives satellite telemetry a large advantage over ground-based systems for the collection of real-time hydrologic data for flood warning, reservoir management, irrigation water control, hydropower generation, and the operation of hydrologic stations.     

THE EFFECT OF FLOOD PLAIN LOCATION ON PROPERTY VALUES: THREE TOWNS IN NORTHEASTERN NEW JERSEY1

ABSTRACT: The persistence of development and settlement in flood plains and continued damages from flooding, raises the question of how property owners respond to flood plain location and whether property values reflect this response. Existing studies disagree on the significance of flood hazard for property values. This study evaluates the effect of flood plain location on assessed valuation and home value in three towns in New Jersey. A t-test on mean assessed value and value of owner-occupied units at block levels showed no statistically significant variation for flood prone and nonflood prone lands. Possible explanations are that homeowners do not know or perceive the risk of living in flood plains, assessors do not incorporate flooding into assessment criteria, and the National Flood Insurance Program subsidies and broadened financial markets may equalize property values.     

Application of Index Procedures to Flood Frequency Analysis in Turkey1

Abstract: This study investigates the regional analysis of annual maximum flood series of 48 stream gauging stations in the basins of the West Mediterranean Region in Turkey. The region is divided into three homogeneous subregions according to both Student‐t test and Dalrymple homogeneity test. The regional relationships of mean annual flood per unit area‐drainage area and coefficient of skew‐coefficient of variation are obtained. Two statistically meaningful relationships of the mean flood per unit area‐drainage area and a unique relationship between skewness and variation coefficients exist. Results show that the index‐flood method may be applicable to each homogenous subregion to estimate flood quantiles in the study area.     

HUMAN BEHAVIOR AND RESPONSE TOWARDS STORM HAZARD IN WEST VANCOUVER,BRITISH COLUMBIA1

ABSTRACT: Human behavior and response towards storm hazard are examined in this study. One-hundred and twenty flood victims in West Vancouver, British Columbia, were administered a sentence completion test to ascertain how these victims behaved and responded to the flash flood of July 12, 1972. The sentence completion test consisted of 11 sentence stems. Seven of these dealt with the respondent's behavior toward the storm experience, and four with the issue of internal vs. external locus of control. Completions of the seven sentence stems at three time situations showed that West Vancouverites expressed the normal reactions of fear and anxiety before the storm; showed negative emotions during the storm; and displayed a feeling of mutual cooperation after the storm. Completions of the remaining four sentence stems revealed that West Vancouverites emphasized the importance of internal factors, viz., autonomy, drive and hard work, in controlling their lives. They recognized God as a benevolent - protective and almighty - powerful figure. Forty percent of the respondents did not believe in luck, while 8 percent regarded it as important in their lives. One might conclude that West Vancouverites could cope with natural hazardous threats better than those who rely on external factors in directing their lives.     

Evaluation of Operational National Weather Service Gridded Flash Flood Guidance over the Arkansas Red River Basin

National Oceanic and Atmospheric Administration's National Weather Service (NWS) flash flood warnings are issued by Weather Forecast Offices and are underpinned by information from the Flash Flood Guidance (FFG) system operated by the River Forecast Centers (RFCs). This study focuses on the quantitative evaluation and limitations of the FFG system using reported flash flood cases in 2010 and 2011. The flash flood reports were obtained from the NWS Storm Event database for the Arkansas‐Red Basin RFC (ABRFC). The current FFG system at the ABRFC provides gridded flash flood guidance (GFFG) system using the NWS Hydrology Laboratory‐Research Distributed Hydrologic Model to translate the upper zone soil moisture to estimates of Soil Conservation Service Curve Numbers. Comparisons of the GFFG and real‐time Multisensor Precipitation Estimator‐derived Quantitative Precipitation Estimate for the same duration and location were used to analyze the success of the system. Typically, the six‐hour duration was characterized by higher probability of detection values than the three‐hour duration, which highlights the difficulty of hydrologic process estimation for shorter time scales. The current system does not take into account physical characteristics such as land use, including irrigated agricultural farm and urban areas, hence, overly dry soil moisture estimates over these areas can lower the success rate of the GFFG product.     

The dilemma of flood control in the United States

In spite of increasing annual expenditures for flood control, losses from flooding continue to rise in the United States. This seeming contradiction arises from overdependence on federally supported structural solutions to flood problems. Nonstructural controls are initiated reluctantly at local levels of government because of constitutional questions, restrictions of local tax bases, lack of federal subsidies for nonstructural solutions, and the high costs of delineating flood hazard areas. The success of the National Flood Insurance Program is doubtful since only about five percent of the flood-prone communities in the United States have qualified for the regular program. Future reduction of flood losses is dependent upon increasing popular awareness of flood hazards and altering federal subsidy policies to reduce the impact of local land-use regulations.     

PREDICTING TEMPORAL AND SPATIAL FLOOD DYNAMICS USING A PRECALIBRATED MODEL1

ABSTRACT: A large storm in December 1990 allowed the evaluation of flood predictions from a hydrologic model (TOPMODEL) that had been previously calibrated on the West Fork of Walker Branch Watershed, a gauged 37.5 ha catchment near Oak Ridge, Tennessee. The model predicts both hydrograph dynamics and the spatial distribution of overland flow using an index based on topography. Maximum extent of overland flow during the storm was determined from patterns of leaf litter removal from valley bottoms. Both the flood hydrograph and the extent of overland flow were accurately predicted using model parameters obtained from a three-month period of normal flow conditions during 1983.     

Adapting cities to climate change – exploring the flood risk management role of green infrastructure landscapes

There is now an emerging sense of the scope and nature of response that can be implemented at building and neighbourhood scales to help adapt cities and urban areas to the changing climate. In comparison, the role of larger natural and semi-natural landscapes that surround and permeate cities is less well understood. Addressing this knowledge gap, this paper outlines two case studies that describe and map the flood risk management functions offered by green infrastructure landscapes situated within the Urban Mersey Basin in North West England. The case studies establish that areas potentially exposed to flooding can be located at some distance, and within different jurisdictions, from upstream areas where the flood hazard may be generated and could be moderated via functions provided by green infrastructure landscapes. This raises planning and governance challenges connected to supporting and enhancing flood risk management functions provided by green infrastructure landscapes.     

Assessing flood mitigation,management, and enforcement using insurance data,California and the USA

Previous research found that National Flood Insurance Program (NFIP) premiums collected in some U.S. states, including California, have far exceeded damage payments. However, this finding raises the question of whether such an imbalance represents systematically good flood management or, instead, merely short-term hydrologic good luck. This study investigated patterns in flood losses on structures that pre-date and post-date the first available flood maps (“pre-Flood Insurance Rate Map [FIRM]” vs. “post-FIRM”) in California, several peer states, and nationwide. California has a larger inheritance of pre-FIRM structures than the national average, apparently reflecting development during the latter half of the 20th Century but before most Federal Emergency Management Agency (FEMA) flood maps. Pre-FIRM properties are a disproportionate cost burden on the system, and the number of pre-FIRM policies has declined over time, but only slowly. Local patterns in pre-FIRM claims suggest targeted areas for enhanced mitigation efforts, including buyouts. Conversely, we find that claims on post-FIRM policies are a reasonable metric of good floodplain management and enforcement, and California's 38% of post-FIRM policies generated just 24% of the state's NFIP claims. Local “post-FIRM claim hotspots” suggest areas to examine more closely. California continues to be a net payer into the National Flood Insurance Program, with $102 million in payouts 2009–2018 versus $2.3 billion in premiums collected, or 4.5 cents of premiums collected for every dollar of premiums. In California, its peer states, and nationwide, future management of flood risk depends on: (1) continued investment in flood control and mitigation of existing floodplain structures, and (2) prudent planning and limitations on new floodplain and coastal development.