Flood Elevation Research Articles

Optimal house elevation for reducing flood-related losses

FEMA recommends that houses in coastal flood zones be elevated to at least 1 foot above the base flood elevation (BFE). However, this guideline is not specific and ignores characteristics of houses that affect their vulnerability. An economically optimal elevation level (OEL) is proposed that minimizes the combined cost of elevation and cumulative insurance premiums over the lifespan of the house. As an illustration, analysis is performed for various coastal houses in Ortley Beach, NJ. Compared with the strategy of raising houses to 1 foot above BFE, the strategy of raising houses to their OELs is much more economical for the homeowners. Elevating to the OELs also significantly reduces government spending on subsidizing low-income homeowners through, for example, a voucher program, to mitigate flood risk. These results suggest that policy makers should consider vulnerability factors in developing risk-reduction strategies. FEMA may recommend OELs to homeowners based on their flood hazards as well as house characteristics or at least providing more information and tools to homeowners to assist them in making more economical decisions. The OEL strategy can also be coupled with a voucher program to make the program more cost-effective.

Flood Risk Assessment of Panchganga River (Kolhapur District, Maharashtra) Using GIS-Based Multicriteria Decision Technique

Flood hazard causes great loss to lives and properties leading to disturbance in human society. Flood is the single most hydrometeorological hazard causing substantial losses. To gain better understanding of the flood phenomena especially for planning and mitigation purposes, flood risk analysis is often required. For the present study, the middle part of Panchganga river of Kolhapur district, Maharashtra was selected. The main objective of the present study was to evaluate the potential flood risk areas of Panchganga river using GIS-based multicriteria decision analysis. The flood scenario across the Panchganga river was analysed using RADARSAT SAR data of 5 August 2005. To remove the speckle of SAR image, a median filtered technique was used. Thresholding technique was applied on RADARSAT SAR data to segregate flooded areas from non-flooded areas. Factors considered for evaluation of the flood risk analysis were flood layer, elevation, infrastructure and land use/ land cover analysis. The spatial multicriteria analysis with ranking, rating and analytical hierarchy process (AHP) method was used to compute the priority weights of each criterion. Accuracy assessment reveals that AHP is the most accurate technique to assess flood risk of Panchganga river.

Measuring Community Resilience: The Role of the Community Rating System (CRS)

Community resilience has become an important concern due to the increasing scale and frequency of natural and technological disasters. Although several frameworks have been introduced to measure resilience, there has been no systematic process that captures all the key sectors of a community. This paper introduces an holistic approach to measure community resilience by specifying the Human, Social, Physical, Natural, Financial and Political sectors of a community [labeled the six capitals (6Cs)] and characterizing four properties of resilience (4Rs) (robustness, resourcefulness, redundancy and rapidity). The 6C-4R framework is linked to the National Flood Insurance Program’s (NFIP) Community Rating System (CRS) that rewards communities for adopting flood risk reduction activities using illustrative examples of resilience strategies adopted by communities and examining the challenges facing the city of New Orleans today after suffering severe losses from Hurricane Katrina. We conclude the paper with a case study of Cedar Rapids, Iowa that joined the CRS in 2010 following a severe flood in 2008. The community has recently undertaken several efforts to reduce future flood losses, notably higher regulatory standards, such as requiring buildings to be higher than the base flood elevation and acquisition and relocation of property to less flood prone areas. Although the CRS captures several sectors of a community, it lacks a measure of social vulnerabilities, which is an important element for community resilience. Future studies are needed to show how one can integrate measures of social vulnerabilities with the CRS for a more holistic view of community resilience.

Progress in operational flood mapping using satellite synthetic aperture radar (SAR) and airborne light detection and ranging (LiDAR) data

During flooding, operational tools for mapping flood extent and depth of water in flood-prone areas are required by those planning emergency response, including UK statutory agencies such as the Environment Agency. Satellite data have become a source of information to map and monitor floods, but many of the methods developed to process the data are unsuitable for accurate, near real-time production of flood information products. This paper describes a new semi-automated methodology developed to provide operational mapping of flood extent and flood depth using satellite synthetic aperture radar (SAR) data combined with light detection and ranging (LiDAR) elevation data. In this method, an analyst uses the flood boundary derived from 8 m spatial resolution satellite SAR data to estimate the flood surface elevation at points around a flooded area using a digital terrain model derived from LiDAR data. This method is compared to a simple satellite ‘SAR-only’ method for generating flood extent and alternative, automated methods of generating flood extent and depth that also used SAR and LiDAR. TerraSAR-X and SPOT 5 data were used from an area including the UK Somerset Levels which suffered a major flood event in February 2014. The new semi-automated method produced similar overall accuracy to the SAR-only method ( Po = 95.8% and Po = 95.3%, respectively), but was more accurate at mapping flood extent where large vegetation or other objects appeared in the satellite SAR data. The automated methods were relatively inaccurate (overall accuracy ranged from Po = 83.4% to Po = 88.8%), but were used to identify where further work on improving the semi-automated-elevation method could be carried out. In addition to the flood extent information provided by the semi-automated-elevation method, flood surface elevation data were produced that could be used to estimated flood depths and flood volumes. The accuracy of the flood elevation surface was tested using LiDAR data acquired of the water surface during the flooding (root mean square error = 0.152 m). The paper discusses progress towards operational flood monitoring using SAR and LiDAR remote sensing products.

유역 치수효과 분석을 통한 재해영향평가의 필요성 제고

This paper shows the effectiveness of flood control by Disaster Impact Assessment Program. In order to prove the usefulness of flood control, this study analyzes the impact of flood control on the area where Disaster Impact Assessment Program had been already applied. The analysis for flood control effectiveness for the development of the area before and after is performed. Also, this study produces the results of the analysis which can point out the problem caused by inspection of following-up control and acceptance of the review in Pre-Disaster Impact Investigation Consultation Program. The results represent flood elevations get lower when the disaster prevention facility was constructed after development than before development because flood runoff was reduced by the disaster prevention facilities. This result means the regulation enforcing construction of disaster prevention facilities in development area is more effective on flood control than the authorization of the empowerment for land-users.

Exploitation of Documented Historical Floods for Achieving Better Flood Defense

Establishing Base Flood Elevation for a stream network corresponding to a big catchment is feasible by interdisciplinary approach, involving stochastic hydrology, river hydraulics, and computer aided simulations. A numerical model calibrated by historical floods has been exploited in this study. The short presentation of the catchment of the Tisza River in this paper is followed by the overview of historical floods which hit the region in the documented period of 130 years. Several well documented historical floods provided opportunity for the calibration of the chosen numerical model. Once established, the model could be used for investigation of different extreme flood scenarios and to establish the Base Flood Elevation. The calibration has shown that the coefficient of friction in case of the Tisza River is dependent both on the actual water level and on the preceding flood events. The effect of flood plain maintenance as well as the activation of six potential detention ponds on flood mitigation has been examined. Furthermore, the expected maximum water levels have also been determined for the case if the ever observed biggest 1888 flood hit the region again. The investigated cases of flood superposition highlighted the impact of tributary Maros on flood mitigation along the Tisza River.

Below the Flood Line

To eliminate a grade crossing of rail lines, the Port of Vancouver USA, in Vancouver, Washington, elected to route a new line to its entrance beneath a bridge carrying a major north–south line. The new line would be well below the 100-year flood elevation of the adjacent Columbia River. To protect it from most flood events, the port constructed an innovative trench structure that will ensure uninterrupted rail service during high water and minimize infiltration from floodwaters.

Street-Scale Modeling of Storm Surge Inundation along the New Jersey Hudson River Waterfront

AbstractA new, high-resolution, hydrodynamic model that encompasses the urban coastal waters of New Jersey along the Hudson River Waterfront opposite New York City, New York, has been developed and validated for simulating inundation during Hurricane Sandy. A 3.1-m-resolution square model grid combined with a high-resolution lidar elevation dataset permits a street-by-street focus to inundation modeling. The waterfront inundation model is a triple-nested Stevens Institute Estuarine and Coastal Ocean Hydrodynamic Model (sECOM) application; sECOM is a successor model to the Princeton Ocean Model family of models. Robust flooding and drying of land in the model physics provides for the dynamic prediction of flood elevations and velocities across land features during inundation events. The inundation model was forced by water levels from the extensively validated New York Harbor Observing and Prediction System (NYHOPS) hindcast of that hurricane.Validation against 56 watermarks and 16 edgemarks provided via the USGS and through an extensive crowdsourcing effort consisting of photographs, videos, and personal stories shows that the model is capable of computing overland water elevations quite accurately throughout the entire surge event. The correlation coefficient (R2) between the watermark observations and the model results is 0.92. The standard deviation of the residual error is 0.07 m. Comparisons to the 16 flood edgemarks suggest that the model was able to reproduce flood extent to within 20 m. Because the model was able to capture the spatial and temporal variation of water levels in the region observed during Hurricane Sandy, it was used to identify the flood pathways and suggest where flood-preventing interventions could be built.

Quantifying bleaching for zero-age fluvial sediment: A Bayesian approach

Luminescence dating of sediment requires the sand grains to have been exposed to sunlight prior to their most recent burial. Under fluvial transport, the amount of sunlight exposure may not always be sufficient to reset the luminescence signal, a phenomenon known as ‘partial bleaching'. The extent of bleaching is dependent on a combination of geomorphic, sedimentological and fluvial processes. If bleaching can be quantified, and the relationship with these processes understood, it could potentially be used as a new environmental proxy for changes in the dynamics of river systems. Here, we use a recently developed statistical model to evaluate the extent of bleaching, by inferring the proportion of well-bleached grains in the small-aliquot population. We sampled low-flow and flood deposits at a single site on the River Sabie, South Africa. We show that the low-flow sediment is almost perfectly bleached (>80% of grains well bleached), while sediment at flood elevations is partially bleached (20–70 % of grains well bleached). The degree of bleaching may show a relationship with flood magnitude as defined by elevation above normal river level, and we speculate on the causes of variability in bleaching between flood samples.

Development of a sequential Artificial Neural Network for predicting river water levels based on Brahmaputra and Ganges water levels

Bangladesh is land of rivers with about 700 km shoreline at the Bay of Bengal. More than 300 rivers flow over the land of Bangladesh having an area of about 1,47,000 km2. A wide part of this country frequently face flood hazard caused by the excessive flow from three major rivers named the Ganges, the Brahmaputra and the Meghna due to heavy monsoon rainfalls on the upstream catchment area. The control of water flow is an international issue shared among Bangladesh, Nepal and India. Among 57 trans-boundary rivers, 54 enter into Bangladesh from India. Seasonal flood management is a regular exercise and costly event in Bangladesh. Among the several tools of flood management, flood forecasting is a major non-structural measure to protect the people and property from the damage of flood. Hence, the water experts of Bangladesh use several water models to assess the flood. All those are hydrodynamic models based on the mathematical framework of the elliptic differential equations. The hydrodynamic models require huge and reliable data to run the model and predict the flood elevations at river cross sections ahead of time. The models are complex and require calibration and validations for geophysical and morphological changes of river cross sections. Flood Forecast Warning Cell forecasts the flood levels during the monsoon period in more than 80 locations spread over the Bangladesh in major rivers which are generated based on boundary water levels at the Ganges, Brahmaputra and estimated rainfalls using rainfall runoff and river models. In order to circumvent the scarcity of reliable and accurate hydrological data, reduce run time and to make faster and simpler flood level prediction, this research investigated a method of using Artificial Neural Network (ANN) to generate the water levels along the rivers at selected locations. The proposed ANN can predict the incoming flood properly using boundary water levels at Bahadurabad in Brahmaputra and at Harding Bridge in the Ganges. The developed ANN has been given the name as `Bangladesh River Artificial Neural Network System' and used to provide an early flood warning system.

Development and uncertainty quantification of hurricane surge response functions for hazard assessment in coastal bays

Reliable and robust methods of extreme value-based hurricane surge prediction, such as the joint probability method (JPM), are critical in the coastal engineering profession. The JPM has become the preferred surge hazard assessment method in the USA; however, it has a high computational cost: One location can require hundreds of simulated storms and more than ten thousand computational hours to complete. Optimal sampling methods that use physics-based surge response functions (SRFs) can reduce the required number of simulations. This study extends the development of SRFs to bay interior locations at Panama City, Florida. Mean SRF root-mean-square errors for open coast and bay interior locations were 0.34 and 0.37 m, respectively, comparable with ADCIRC errors. Average uncertainty increases from open coast, and bay SRFs were 10 and 12 %, respectively. Long-term climate trends, such as rising sea levels, introduce nonstationarity into the simulated and historical surge datasets. A common approach to estimating total flood elevations is to take the sum of projected sea-level rise (SLR) and present day surge (static approach); however, this does not account for dynamic SLR effects on surge generation. This study demonstrates that SLR has a significant dynamic effect on surge in the Panama City area, and that total flood elevations, with respect to changes in SLR, are poorly characterized as static increases. A simple adjustment relating total flood elevation to present day conditions is proposed. Uncertainty contributions from these SLR adjustments are shown to be reasonable for surge hazard assessments.

New York City Panel on Climate Change 2015 Report. Chapter 3: Static coastal flood mapping.

New York City Panel on Climate Change 2015 Report. Chapter 3: Static coastal flood mapping.

The Impact of Tidal Phase on Hurricane Sandy's Flooding Around New York City and Long Island Sound

How do the local impacts of Hurricane Sandy's devastating storm surge differ because of the phase of the normal astronomical tide, given the spatiotemporal variability of tides around New York? In the weeks and months after Hurricane Sandy's peak surge came ashore at the time of local high tide at the southern tip of Manhattan and caused record-setting flooding along the New York and New Jersey coastline, this was one question that government officials and critical infrastructure managers were asking. For example, a simple superposition of the observed peak storm surge during Sandy on top of high tide in Western Long Island Sound comes within 29 cm (less than a foot) of the top elevation of the Stamford Hurricane barrier system which would have been overtopped by 60 cm surface waves riding over that storm tide. Here, a hydrodynamic model study of how shifts in storm surge timing could have influenced flood heights is presented. Multiple flood scenarios were evaluated with Stevens Institute of Technology's New York Harbor Observing and Prediction System model (NYHOPS) having Hurricane Sandy arriving any hour within the previous or next tidal cycle (any hour within a 26-hour period around Sandy's actual landfall). The simulated scenarios of Sandy coming between 7 and 10 hours earlier than it did were found to produce the worst coastal flooding in the Upper East River, Western and Central Long Island Sound among the evaluated cases. Flooding would have generally been worse compared to the real Sandy in Connecticut and the areas of New York City around the Upper East River between the boroughs of Queens and the Bronx, exceeding record flood heights. However, the New York Harbor region would still have seen its record flood elevation exceeded, so the storm's impact could have been more widespread. The hydrodynamic model results suggest that the still-water levels would have risen to within 75 cm of the top elevation of the Stamford storm surge barrier, 46 cm lower than the naïve superposition of astronomical tide and storm surge.

Risk factors for foot-and-mouth disease in Zambia, 1981–2012

The aim of this study was to describe the spatial distribution of foot-and-mouth disease (FMD) outbreaks in Zambia for the period January 1981–December 2012 and to quantify the association between geographical features (proximity to roads, national parks, wetland areas) and the spatial distribution of FMD using a Poisson point process model.Details of FMD outbreaks retrieved from the Zambian Department of Veterinary and Livestock Development included the date of onset of clinical signs and the name of the ward in which the index case enterprise was located. A total of 62 FMD outbreaks occurred throughout the study period. Outbreaks occurred in the south of the Southern province along the border with Namibia and Botswana (n=5), in the Western province (n=2), in the Southern and Central provinces on the Kafue flood plains (n=44), and in the north east of the country close to the border with Tanzania (n=11). Increases in distance to the nearest major international border crossing, distance to the nearest major road, distance to the wetland area of the Kafue flood plain, wetness index and elevation were all associated with a decrease in FMD-outbreak ward intensity. Our analyses support the hypothesis that in drier areas of the country cattle are more likely to aggregate around communal drinking pools. Aggregation of cattle provides conditions suitable for FMD spread and detection.

Simulations of Hurricane Katrina (2005) under sea level and climate conditions for 1900

Global warming may result in substantial sea level rise and more intense hurricanes over the next century, leading to more severe coastal flooding. Here, observed climate and sea level trends over the last century (c. 1900s to 2000s) are used to provide insight regarding future coastal inundation trends. The actual impacts of Hurricane Katrina (2005) in New Orleans are compared with the impacts of a similar hypothetical hurricane occurring c. 1900. Estimated regional sea level rise since 1900 of 0.75 m, which contains a dominant land subsidence contribution (0.57 m), serves as a ‘prototype’ for future climate-change induced sea level rise in other regions. Landform conditions c. 1900 were estimated by changing frictional resistance based on expected additional wetlands at lower sea levels. Surge simulations suggest that flood elevations would have been 15 to 60 % lower c. 1900 than the conditions observed in 2005. This drastic change suggests that significantly more flood damage occurred in 2005 than would have occurred if sea level and climate conditions had been like those c. 1900. We further show that, in New Orleans, sea level rise dominates surge-induced flooding changes, not only by increasing mean sea level, but also by leading to decreased wetland area. Together, these effects enable larger surges. Projecting forward, future global sea level changes of the magnitude examined here are expected to lead to increased flooding in coastal regions, even if the storm climate is unchanged. Such flooding increases in densely populated areas would presumably lead to more widespread destruction.

재귀호출 알고리듬 기반의 홍수전파 특성 분석

본 연구에서는 무주 남대천을 대상으로 재귀호출 알고리듬을 이용하여 제방 파제시 홍수위별 홍수전파 특성을 분석하였다. 먼저 벙구보와 차산보를 파제 지점으로 설정하여 재귀호출 알고리듬에 의한 홍수위별 홍수전파 차수를 분석하였으며, 홍수전파 차수별 격자수와 누계 침수면적을 계산하였다. 또한 홍수전파 차수와 DEM 격자크기를 기준으로 홍수위별로 홍수가 전파되는 시간을 계산하였다. 재귀호출 알고리듬에 의한 홍수전파 차수의 분포특성을 통해 홍수 전파 과정을 파악할 수 있었으며, 홍수전파 차수별 누계 침수면적 그래프의 기울기 패턴을 통해 홍수에 취약한 지역을 선정함으로써 수재해 업무에 기초자료로 제공할 수 있었다. 또한 홍수위별로 홍수전파 시간을 계산함으로써 홍수시 주민들의 대피경로 및 대피시간과 같은 계획을 수립하는데 매우 효과적인 정보를 제공해 줄 수 있을 것으로 판단된다. This paper analyzed the flood propagation characteristics of each flood elevation due to failure of embankment in Muju Namdae Stream using recursive call algorithm. A flood propagation order by the flood elevation was estimated by setting destruction point at Beonggu and Chasan small dam through recursive call algorithm and then, the number of grids of each flood propagation order and accumulated inundation area were calculated. Based on the flood propagation order and the grid size of DEM, flood propagation time could be predicted each flood elevation. As a result, the study could identify the process of flood propagation through distribution characteristic of the flood propagation order obtained from recursive call algorithm, and could provide basic data for protection from flood disaster by selecting the flood vulnerable area through the gradient pattern of the graph for accumulated inundation area each flood propagation order. In addition, the prediction of the flood propagation time for each flood water level using this algorithm helped provide valuable information to calculate the evacuation path and time during the flood season by predicting the flood propagation time of each flood water level.

The Long Road to Recovery: Environmental Health Impacts of Hurricane Sandy

Building contractor John Pierciey stands in the gutted interior of a 1950s-era home in Manasquan, New Jersey. Wallboard, two layers of wood flooring, a layer of felt—all of it had to be ripped out to rid the house of mold caused by Hurricane Sandy’s storm surge. “This is the sixth house I’ve gutted in a week,” Pierciey says. “Every one is different. You don’t know what you’re going to find until you take them apart.” Residents and volunteers keep warm by a fire barrel in the New Dorp Beach neighborhood of Staten Island, 5 November 2012. Power outages persisted through a cold snap that put temperatures in the single digits. So it is with the environmental health impacts of Hurricane Sandy. Every layer of society, every type of building, has felt the impact of the storm, which struck the U.S. East Coast on 29 October 2012. Incidences of death and illness, though small in number compared with some storms, have come in many forms, the effects still unfolding as time goes by.

Implications, Planning, and Design Considerations for Rising Sea Levels at the Coast

Implications, Planning, and Design Considerations for Rising Sea Levels at the Coast

COMBINING COASTAL DESIGN-FLOOD ELEVATIONS AND SEA LEVEL RISE PROJECTIONS

Design-flood elevations with associated exceedance probabilities are often determined for coastal projects. Rising sea level introduces another design consideration that needs to be combined with the design-flood level. However, most sea level projections do not have exceedance probabilities that can be used in conjunction with the design flood to obtain total flood elevations with exceedance probabilities. This paper shows how to combine design-flood elevations with sea level rise projections that have exceedance probabilities, such as those of the Intergovernmental Panel for Climate Change (Bindoff et al 2007) or Houston (2012a), to obtain total elevations at desired exceedance probabilities over particular intervals.

Numerical Modeling of Tsunami Wave Run-Up and Effects on Sediment Scour around a Cylindrical Pier

AbstractThe linked two-dimensional hydrodynamic and sediment-scour models have been enhanced to simulate tsunami wave run-up on a sloping beach to determine its effects on sediment scour around a cylinder pier located in the wave breaking and run-up zone. To resolve the steep wavefront of the tsunami bore, the kinetic flux vector splitting scheme was adopted to solve the hydrodynamic model equations in the unstructured triangular mesh. The models have been validated by comparing model simulations with experimental data. The results indicate that the model predictions of water surface elevations and velocity match well with the measured data. The error for peak flood elevation ranges from 0.01 to 0.11 m, and the maximum error for the peak velocity is 6%. The model simulations adequately characterize the tsunami wave propagations and transformations as the wave approaches the beach from offshore, especially for the sharp tsunami front before it breaks and the tsunami bore runs up in the beach slope. The mod...