FLOOD HAZARD IDENTIFICATION AND FLOOD PLAIN MANAGEMENT ON ALLUVIAL FANS1

ABSTRACT: Recognition of the flood hazard that exists on alluvial fans has seriously lagged behind the recognition of other more conventional flood hazards such as those associated with most rivers. This delay in recognition was due, until recently, to a general lack of economic investment and development in these areas and a concomitant lack of historical alluvial fan flood damage. Dramatic recent events, such as Tropical Storm Kathleen, emphasized to the Federal Insurance Administration (FIA) the need for developing an appropriate methodology to identify flood hazard areas on alluvial fans. This paper presents the methodology now employed by FIA as well as flood plain management considerations that could reduce future flood related damage to communities developing in these areas.     

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.     

An Analysis of the Effects of Land Use and Land Cover on Flood Losses along the Gulf of Mexico Coast from 1999 to 2009

Major coastal flooding events over the last decade have led decision makers in the United States to favor structural engineering solutions as a means to protect vulnerable coastal communities from the adverse impacts of future storms. While a resistance‐based approach to flood mitigation involving large‐scale construction works may be a central component of a regional flood risk reduction strategy, it is equally important to consider the role of land use and land cover (LULC) patterns in protecting communities from floods. To date, little observational research has been conducted to quantify the effects of various LULC configurations on the amount of property damage occurring across coastal regions over time. In response, we statistically examine the impacts of LULC on observed flood damage across 2,692 watersheds bordering the Gulf of Mexico. Specifically, we analyze statistical linear regression models to isolate the influence of multiple LULC categories on over 372,000 insured flood losses claimed under the National Flood Insurance Program per year from 2001 to 2008. Results indicate that percent increase in palustrine wetlands is the equivalent to, on average, a $13,975 reduction in insured flood losses per year, per watershed. These and other results provide important insights to policy makers on how protecting specific types of LULC can help reduce adverse impacts to local communities.     

FLOODPLAINS AND HOUSING VALUES: IMPLICATIONS FOR FLOOD MITIGATION PROJECTS1

ABSTRACT: The hedonic valuation method was used to quantify the impact of floodplain location on housing values in Fargo‐Moor‐head. Being located in the 100‐year floodplain lowered the home values by $8,990, and such homes were worth $10,241 less than similar homes located outside the floodplain before the major flood event of 1997. Required flood insurance premiums for these homes were determined to account for approximately 81 percent of this price depreciation. In contrast, homes in the 500‐year floodplain were worth $3,100 more than similar homes not in the floodplain. It was concluded that more disclosure is needed regarding the location of the 500‐year floodplain, and that the hedonic valuation method can be used to calculate the economic gains and losses associated with flood mitigation projects or floodplain remapping efforts that result in the reclassification of the legal floodplain status of individual homes.     

Coastal Management of Failaka Island, Kuwait

Failaka Island is one of the most important islands belonging to the State of Kuwait. With the Iraqi invasion of Kuwait on 2 August 1990, most of the activies on Failaka Island were destroyed. After the liberation of Kuwait, the Kuwaiti government decided to reconstruct the island for touristic and recreational purposes. Thus, a coastal development plan was needed. The presented study is an attempt to address the coastal zone management of the island. Based on the overall geomorphological features of the island, the coast was classified into four coastal zones. The wave and tidal conditions were identified around the island. The major items controlling the coastal development were specified. Accordingly, a detailed coastal zone management map for future development was developed. The overall goal was to provide decision-makers with guidelines for the future development of the island.     

A NONTRADITIONAL METHODOLOGY FOR FLOOD STAGE-DAMAGE CALCULATIONS1

ABSTRACT: This paper presents a new methodology to calculate economic losses from hypothetical, extreme flood events, such as the Probable Maximum Flood. The methodology uses economic data compiled from already-available secondary sources, such as U.S. Census data on magnetic tapes, utilizing microcomputer and other electronic media. Estimates of land elevations are obtained from topographic maps, and flood elevations axe estimated using, for example, a dam breach and flood routing (DAMBRK) model (Fread, 1984). The calculations are performed at a disaggregate spatial scale, by various land use and industrial classification categories. The basic areal units are city blocks (for urbanized areas), enumeration districts, and Census tracts. Depth-damage functions, which provide an estimate of damages as a proportion of the existing value of the structure, are estimated statistically. Computer software (called DAMAGE) is used to combine the economic, flood elevation, and depth-damage information to compute economic losses for different possible flood stages and for different inflow events. Two case studies are presented as illustrations of the method.     

新时代生态环境建设中陆海统筹发展对策研究——以厦门为例

海岸带地区是陆海交互作用区,是陆海统筹中需要重点关注的区域,党的十九大报告里提出要坚持陆海统筹,《深化党和国家机构改革方案》中提出整合原环境保护部等部委的相关污染防治和生态保护执法及国家海洋局的海洋环境保护职责,组建生态环境部。本研究通过对厦门市陆海统筹政策现状系统梳理分析,厘清生态环境建设中陆海统筹的关键问题,总结出陆海统筹工作的对策建议,包括构建生态环境陆海统筹管理新模式、蓝色经济与生态文明协同发展新模式、基于绿色发展的弹性海岸新模式、"三个一"智慧海岸带大数据信息系统技术新体系等。这些对策对于我国海岸带城市区域生态环境建设的陆海统筹和海岸带综合管理工作具有借鉴意义。     

论我国海岸带立法的核心内容

2018年11月18日发布的《中共中央国务院关于建立更加有效的区域协调发展新机制的意见》明确提出了"推动海岸带管理立法"的工作要求。该工作的重心理应是解决目前我国海岸带管理实践中的突出问题，即陆海之间、部门行业之间和行政辖区之间难以统筹协调的问题。解决该问题的有效途径是通过立法的方式构建统筹协调机制。美国海岸带管理制度中的统筹协调机制颇具特色，由"总协调人"和"联络人"制度、"联邦一致性"制度、州海岸带管理项目与州其他项目的统筹协调制度，以及陆海统筹协调制度等方面组成。我国可以借鉴其成功经验，在海岸带立法中，以构建统筹协调机制为核心内容。该机制以程序性规则为主体，设立"总协调人"和"联络人"制度，组成统筹协调网络，并规定统筹协调的基本"排序规则"。     

FLOOD EVENT MODELING - A STUDY OF TWO METHODS1

: Despite the advances in catchment modeling in recent years, engineers still face major problems in estimating flood flows. Application of unit hydrograph and runoff routing models to five United Kingdom catchments shows that either can be tuned to predict, on a test event, the routing effects of a catchment with equal accuracy. The larger remaining problem is the prediction of losses from rainfall and this study shows how alternative ways of describing the within event distribution of these losses can be an important factor controlling the success of the overall model. Other problems include the risks of extrapolation to larger events, baseflow separation methods, rainfall patterns, and inevitable errors in the data.     

COMPREHENSIVE FLOOD PLAIN MANAGEMENT1

Flooding and the susceptibility to flood damage inherent in all land uses constitute the flood hazard. Resolution of the hazard while properly recognizing flood plain environmental attributes within the context of overall community or area needs is the essence of comprehensive flood plain management. The traditional approach–flood control–has effected modification of only the flooding component of the hazard whether it be coastal or inland. Until recently Federal programs have overlooked the possibilities of modifying the susceptibility component, for which the major responsibility lies with non-Federal interests. Beginning with actions in the TVA area, the latter is now being strongly encouraged through Federal programs and actions notably the Flood Plain Management Services and Survey Programs of the Corps of Engineers, those stemming from Executive Order 11296, and those required for eligibility under the National Flood Insurance Act of 1968. Flood plain management objectives must be stated in planning, e.g., economic efficiency, reduction in threat to life and health, environmental improvement, and regional development, to permit proper evaluation of the optional means and approaches for achieving them.     

The impact of tidal flooding on a coastal community in Semarang, Indonesia

The article presents household vulnerability, local community adaptive capacity, and government’s response to tidal flood hazard in the Semarang coastal area, Central Java Province, Indonesia. Using data gathered from a survey of households, the study revealed a number of important factors about the interaction between people and flood. The coastal community has been experiencing problems related to tidal floods. They have adapted to tidal flooding with structural measures, such as increasing the floor level, making small dams in front of houses, increasing yard and street levels in the neighborhood area, and creating dykes around residential areas. Tidal flood mitigation in the Semarang coastal area should incorporate governmental action and local community capacities for proper protection of the population.     

Non-linear incentives,plan design,and flood mitigation: the case of the Federal Emergency Management Agency's community rating system

A basic proposition of ‘agency theory’ is that output-based performance incentives encourage greater effort. However, studies find that incentive schemes can distort effort if rewards for performance are discrete or non-linear. The Federal Emergency Management Agency's (FEMA) Community Rating System (CRS) is a flood mitigation programme with a non-linear incentive design. Under this programme, localities are incentivised to implement a mix of 18 flood mitigation activities. Each activity is performance scored, with accumulated scores corresponding to a percent discount on flood insurance premiums for residents that hold National Flood Insurance policies. Discounts range from 0 to 45% and increase discretely in increments of 5%. With multivariate statistical and Geographic Information Systems analytic techniques, tests are made to find whether observed changes in annual CRS scores for participating localities in Florida are explained by non-linear incentives, adjusting for hydrologic conditions, flood disaster histories, socio-economic and human capital controls that can plausibly account for local mitigation activity scores over time. Results indicate that local jurisdictions are discount-seeking, with mitigation efforts partially driven by the non-linear incentive design of the CRS programme. The paper ends with recommendations to improve the operation FEMA's flood mitigation programme.     

Flood Risk Reduction from Agricultural Best Management Practices

Best management practices (BMPs) play an important role in improving impaired water quality from conventional row crop agriculture. In addition to reducing nutrient and sediment loads, BMPs such as fertilizer management, reduced tillage, and cover crops could alter the hydrology of agricultural systems and reduce surface water runoff. While attention is devoted to the water quality benefits of BMPs, the potential co‐benefits of flood loss reduction are often overlooked. This study quantifies the effects of selected commonly applied BMPs on expected flood loss to agricultural and urban areas in four Iowa watersheds. The analysis combines a watershed hydrologic model, hydraulic model outputs, and a loss estimation model to determine relationships between hydrologic changes from BMP implementations and annual economic flood loss. The results indicate a modest reduction in peak discharge and economic loss, although loss reduction is substantial when urban centers or other high‐value assets are located downstream in the watershed. Among the BMPs, wetlands, and cover crops reduce losses the most. The research demonstrates that watershed‐scale implementation of agricultural BMPs could provide benefits of flood loss reduction in addition to water quality improvements.     

USING GEOLOGY TO IMPROVE FLOOD HAZARD MANAGEMENT ON ALLUVIAL FANS ‐ AN EXAMPLE FROM LAUGHLIN,NEVADA1

A study of the piedmont of the Newberry Mountains near Laughlin, Nevada, demonstrates that geologic information can improve the scientific basis of flood‐hazard management on alluvial fans in desert areas. Comparison of geologic information against flood insurance rate maps (FIRMs) reveals flaws in conventional methods for flood hazard delineation in this setting. Geologic evidence indicates that large parts of the Newberry piedmont have been isolated from significant flooding for at least the past 10,000 years. This contrasts with existing FIRMs that include large tracts of nonflood prone land in the 100‐year and 500‐year flood hazard zones and exclude areas of indisputably flood prone land from the regulatory flood plain. From the basis of the geology, flood hazards on at least one‐third of the piedmont are mischaracterized on the regulatory maps. The formal incorporation of geologic data into flood hazard studies on desert piedmonts could significantly reduce this type of discrepancy and substantially reduce the scope, hence cost, of more elaborate engineering studies and hazard mitigation strategies. The results of this study affirm the value of new Federal Emergency Management Agency (FEMA) recommendations for characterizing alluvial fan flood hazards and support an argument for mandating geological studies in the regulatory process.     

Flood problems in Bangladesh: Is there an indigenous solution?

Bangladesh, situated on the delta of the Ganges, the Brahmaputra, and the Meghna rivers, experiences two distinct types of inundations: (a) river floods resulting from excessive runoff contributed by monsoon precipitation and (b) coastal floods induced by storm surges of tropical cyclones. The river floods are normal annual events and human settlements and agricultural practices have adapted admirably well to their regimes. Abnormal floods that occur once in every few years cause serious damage to crops and properties. To minimize flood losses, a number of modern engineering projects have been constructed within Bangladesh. However, the successful solution of the problem would probably require some international collaboration for basinwide unified systems planning, since large parts of the drainage basins of Bangladesh lie beyond its borders. In the absence of such collaboration, internal resources should be utilized for the construction of smaller public projects, such aspolders, and for encouraging and reinforcing various types of indigenous adjustments to floods. There are very few successful indigenous adjustments to coastal floods. Most of the structural solutions, such as community shelters and higher embankments, are expensive public projects that are probably beyond the means of the internal resources of the country.     

A Probabilistic,Parcel‐Level Inundation Prediction Tool for Medium‐Range Flood Forecasting in Large Lake Systems

This study contributes a bathtub‐style inundation prediction model with abstractions of coastal processes (i.e., storm surge and wave runup) for flood forecasting at medium‐range (weekly to monthly) timescales along the coastline of large lakes. Uncertainty from multiple data sources are propagated through the model to establish probabilistic bounds of inundation, providing a conservative measure of risk. The model is developed in a case study of the New York Lake Ontario shoreline, which has experienced two record‐setting floods over the course of three years (2017–2019). Predictions are developed at a parcel‐level and are validated using inundation accounts from an online survey and flyover imagery taken during the recent flood events. Model predictions are compared against a baseline, deterministic model that accounts for the same processes but does not propagate forward data uncertainties. Results suggest that a probabilistic approach helps capture observed instances of inundation that would otherwise be missed by a deterministic inundation model. However, downward biases are still present in probabilistic predictions, especially for parcels impacted by wave runup. The goal of the tool is to provide community planners and property owners with a conservative, parcel‐level assessment of flood risk to help inform short‐term emergency response and better prepare for future flood events.     

Pressures,trends, and impacts in coastal zones: Interactions between socioeconomic and natural systems

This paper assesses the status of coastal zones in the context of expected climate change and its related impacts, as well as current and future socioeconomic pressures and impacts. It is argued that external stresses and shocks relating to sea-level rise and other changes will tend to exacerbate existing environmental pressures and damage in coastal zones. Coastal zones are under increasing stress because of an interrelated set of planning failures including information, economic market, and policy intervention failures. Moves towards integrated coastal zone management are urgently required to guide the coevolution of natural and human systems. Overtly technocentric claims that assessments of vulnerability undertaken to date are overestimates of likely future damages from global warming are premature. While it is the case that forecasts of sea-level rise have been scaled down, much uncertainty remains over, for example, combined storm, sea surge, and other events. In any case, within the socioeconomic analyses of the problem, resource valuations have been at best only partial and have failed to incorporate sensitivity analysis in terms of the discount rates utilized. This would indicate an underestimation of potential damage costs. Overall, a precautionary approach is justified based on the need to act ahead of adequate information acquisition, economically efficient resource pricing and proactive coastal planning.     

LUMP SUM TAX LOSS REIMBURSEMENT UNDER THE THAMES RIVER FLOOD CONTROL COMPACT1

ABSTRACT: Under the terms of the Thames River Valley Flood Control Compact, Connecticut has been paying Massachusetts 40 percent of the annual property tax losses suffered by seven Massachusetts towns where four flood control structures were located. The permissable alternative of a single lump sum payment was investigated in the study summarized here. The lump sum payment should be the proportion of total benefits (flood control and recreation) from the four structures which Connecticut receives, multiplied by the present value of projected tax losses in the seven tom Flood control benefits and their distribution between the two states were fixed in the Compact, but a survey was necessary to determine recreational benefits and their distribution. Regression analysis of 1957 to 1978 tax loss data provided equations used to project future tax losses. Resent values of projected tax low were calculated using discount rates ranging from 6 to 12 percent. A plausible range of lump sum reinbursements as of 1979 was identified.     

DEVELOPMENT OF A GIS‐BASED FLOOD INFORMATION SYSTEM FOR FLOODPLAIN MODELING AND DAMAGE CALCULATION1

ABSTRACT: This work presents a flexible system called GIS‐based Flood Information System (GFIS) for floodplain modeling, flood damages calculation, and flood information support. It includes two major components, namely floodplain modeling and custom designed modules. Model parameters and input data are gathered, reviewed, and compiled using custom designed modules. Through these modules, it is possible for GFIS to control the process of flood‐plain modeling, presentation of simulation results, and calculation of flood damages. Empirical stage‐damage curves are used to calculate the flood damages. These curves were generated from stage‐damage surveys of anthropogenic structures, crops, etc., in the coastal region of a frequently flooded area in Chia‐I County, Taiwan. The average annual flood damages are calculated with exceedance probability and flood damages for the designed rainfalls of 2, 5, 10, 25, 50, 100, and 200 year recurrence intervals with a duration of 24 hours. The average annual flood depth in this study area can also be calculated using the same method. The primary advantages of GFIS are its ability to accurately predict the locations of flood area, depth, and duration; calculate flood damages in the floodplain; and compare the reduction of flood damages for flood mitigation plans.     

Re-thinking relationships between environmental attitudes and values for effective coastal natural resource management in Ghana

The coastal zone of Ghana is home to about a quarter of the total population of the country and its importance has been well emphasised in policy documents, such as the Ghana Shared Growth and Development Agenda, the National Climate Change Policy as well as the National Environmental Policy. However, environmental degradation remains a critical issue as dependence on coastal natural resources continues to increase, and its effect is being felt more strongly by certain groups than others. This paper identifies women as key stakeholders, and through an empirical assessment highlights the need to factor their environmental attitudes and values into efforts to manage the coast in an integrated manner. The results show that respondents generally had positive environmental attitudes, which did not translate to good environmental behaviour. Respondents placed the greatest importance on the coastal natural resources as sources of wealth creation and of food, values which are often described as being “anthropocentric”. Hence, initiatives that could win the support of the local people and also help manage coastal resources effectively are those that link the livelihoods and well-being to coastal natural resource management.