Flood Hazard Areas Research Articles

Evaluating the effects of local floodplain management policies on property owner behavior

Floodplain management programs have been adopted by more than 85% of local governments in the nation with designated flood hazard areas. Yet, there has been little evaluation of the influence of floodplain policies on private sector decisions. This article examines the degree to which riverine floodplain management affects purchase and mitigation decisions made by owners of developed floodplain property in ten selected cities in the United States. We find that the stringency of such policies does not lessen floodplain property buying because of the overriding importance of site amenity factors. Indeed, flood protection measures incorporated into development projects appear to add to the attractiveness of floodplain location by increasing the perceived safety from the hazard. Property owner responses to the flood hazard after occupancy involve political action more often than individual on-site mitigation. Floodplain programs only minimally encourage on-site mitigation by the owner because most owners have not experienced a flood and many are unaware of the flood threat. It is suggested that floodplain programs will be more effective in meeting their objectives if they are directed at intervention points earlier in the land conversion process.

Liability as a Dilemma for Local Managers

Local governments may be sued if they tightly regulate uses in flood, erosion, avalanche, or natural hazard areas, or undertake other mitigation measures. They may also be sued if they issue permits for hazardcausing uses, increase natural or technological hazards, or fail to design or maintain adequately mitigation measures such as flood control works. How should local governments react to this dual and often serious threat of litigation? Given the current trends in the courts, are immediate constitutional challenges and claims for damages or long-term suits a greater potential problem? How can the chances of high jury awards, which can bring a local government to the verge of bankruptcy, be avoided? The following discussion focuses on this action, no action dilemma not only because it is an increasingly important issue for local governments, but because the dilemma illustrates a broad range of legal issues in hazards management.' The discussion of legal issues and trends in the courts begins with an overview of hazards litigation. Constitutional challenges to government issuance or denial of permits, planning, zoning, mitigation measures are then considered. Liability suits and trends in litigation are next examined. Finally, strategies for reducing potential liability are suggested.

Book Review: Regulation of Flood Hazard Areas to Reduce Flood Losses, Volume 3

Book Review: Regulation of Flood Hazard Areas to Reduce Flood Losses, Volume 3

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.

Relationship between alluvial soils and flooding in the Piedmont lowland of southeastern Pennsylvania

Regressions of 50‐ and 100‐year synthetic flood widths on widths of alluvial soils bordering the stream were computed with confidence intervals for data from streams in the Piedmont Lowland of southeastern Pennsylvania. These intervals were too wide to recommend use of alluvial soils in floodplain zoning in this gently rolling terrain. A rule of thumb of 2½ times the alluvial soils width was suggested for safe location of land uses for which flooding would be intolerable. Data for one of the minor soils indicated that some soils may delineate flood hazard areas better than others, but too few data were available for complete analysis.

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.

Dealing with Variable Flood Hazard

The National Flood Insurance Program administered by the Federal Insurance Administration, HUD-FHA Minimum Property Standards, and most local flood plain management programs define flood hazard areas as lands inundated by the 100-yr flood. Curves are developed that can be used to manage flood plain load on an equal damage exposure basis given the stage-frequency relationship for the flood plain and the stage-damage relationship for each property. The issue of accentable damage exposure is considered through comparisons with fire insurance rates, property taxes, and rates of return on property investments. An examination of the difference between the two indices shows that the equity advantage of management on the basis of damage exposure can be balanced with the administrative advantage of regulation on a frequency basis by continuing to use frequency but varying the return period used according to the damage exposure. /Author/

Hydrogeomorphic methods for the regional evaluation of flood hazards

The “upstream” approach to flood hazard evaluation involves the estimation of hydrologic response in small drainage basins. This study demonstrates the application of geomorphology to such studies in a region of unusually intense flooding in central Texas. One approach to flood hazard evaluation in this area is a parametric model relating flood hydrograph characteristics to quantitative geomorphic properties of the drainage basins. A preliminary model uses multiple regression techniques to predict potential peak flood discharge from basin magnitude, drainage density, and ruggedness number. After mapping small catchment networks (4 to 20 km2) from remote sensing imagery, input data for the model are generated by network digitization and analysis by a computer-assisted routine of watershed analysis. The study evaluated the network resolution capabilities of the following data formats: (1) large-scale (1:24,000) topographic maps, employing Strahler's “method of v's”, (2) low altitude black-and-white aerial photography (1:13,000 and 1:20,000 scales), (3) NASA-generated aerial infrared photography at scales ranging from 1:48,000 to 1:123,000, and (4) Skylab Earth Resources Experiment Package S-190A and S-190B sensors (1:750,000 and 1:500,000 respectively). Measured as the number of first order streams or as the total channel length identified in small drainage areas, resolution is strongly dependent on basin relief. High-density basins on the Edwards Plateau were poorly depicted on orbital imagery. However, the orbital network definition of low-relief basins on the inner Texas Coastal Plain is nearly as accurate as results from large-scale topographic maps. Geomorphic methods are also useful for flood hazard zonation in “downstream” flood plain areas. Studies of the Colorado River valley near Austin, Texas, easily distinguished infrequent (100- to 500-year recurrence interval), intermediate (10- to 30-year), and frequent (1- to 4-year) hazard zones. These mapping techniques are especially applicable to the rapid regional evaluation of flood hazards in areas for which there is a lack of time and money to generate more accurate engineering-hydraulic flood hazard maps.

Flood Insurance as a Component of Land Use Management

Floods will continue to cause damage as long as development continues upon flood-prone lands. Inevitably, flooding occurs, damage ensues and there is personal suffering and loss. A burden of rescue and relief operations falls on all taxpayers.Flood control projects cannot protect against all damage, and not all flood hazard areas are amenable to flood control projects. An alternative to continued construction of engineering works for flood protection is flood plain management. To be effective, this must be brought about through political and legal means. Its purposes are to minimize the consequences of flooding and to achieve, in the long run, an optimum use of the flood plains.

Flood Proofing Regulations for Building Codes

Few of the building codes used by urban communities require flood proofing of new or existing structures as a condition for flood hazard area construction or occupancy. The codes provide only minimum standards to regulate and control the design and construction of all buildings to safeguard life, health, property, and public welfare. Man's ever increasing encroachment into the flood plains has tremendously increased the flood damage potential and hazard to the users. This has pointed out the urgent need to regulate the use of flood plains, types of structures permitted, and special design and construction standards to be met if flood damage reduction is to become a reality. Zoning and flood-plain regulations can effectively regulate flood-plain occupancy and types of structures permitted. Flood proofing regulations in building codes can provide the special criteria needed to assure quality flood damage free constructions.

Legal Problems in Regulating Flood Hazard Areas

Effective flood plain management programs must appropriately combine structural and nonstructural measures. An effective nonstructural technique involves the placement of restrictions by legislative bodies upon private and public uses in flood hazard areas. Such restrictions prohibit obstructions in floodways and guide and restrict development in floodway fringe areas. The likelihood that flood hazard regulations will be more widely adopted has increased with the publication by the Water Resources Council of model statutes and ordinances for flood hazard reduction, the implementation of the federal flood insurance program, and the possibility of federal grants for land use planning. Even if such regulations are adopted, they must not conflict with legal and constitutional requirements of equal protection and due process of law. Courts have been reluctant to uphold severe restrictions on the use of a person's land when other economic uses are not possible or where the degree of hazard is small related to the severity of the restrictions imposed.

State Flood-Plain Management Activities

Although billions of dollars have been spent for the control of floods, it has been amply demonstrated that, on a nationwide basis, the effort to reduce flood damages is being lost. The flood control program's inability to maintain its early advantage is primarily attributable to rapidly increasing development on flood plain lands. The Tennessee Valley Authority pioneered the comprehensive flood damage prevention concept, portions of which have served as models for later endeavors by various states. Activities by 10 selected states in flood plain identification and management are cited as examples of the concept's past and continuing evolution. Most active state efforts are oriented toward providing adequate identification of flood plains and assisting local entities in implementing appropriate management of designated flood hazard areas. Technical, administrative, and legal problems are noted, as well as similarities to other social and economic needs of society.

Spray Irrigation and the Water Resources Act, 1963

The Water Resources Act (I963) in England and Wales has brought about some valuable innovations in the field of water-resource management. Among them the charging scheme is particularly challenging, for it attempts to assess the effect of each abstraction upon the general water resource and upon other legitimate users. The purpose of this article is to assess the charging scheme as a management tool, and to appraise in particular the manner in which it may be used to guide decisions in the use of water for spray irrigation. The major findings of the study point to certain difficulties in managing the present and future demands for spray irrigation. The policy adopted by most river authorities to require future irrigators to provide private sources of supply appears highly satisfactory, though substantial demands are still made by direct abstractors operating under prescriptive licences of right. This latter group, whose demands must be met (at least in moderately dry years), may seek augmentation of river flow to safeguard their licences. It is shown that their perception of alternative management techniques is not readily influenced either by the charging scheme or by institutional guides. It is also shown that the imposition of the charging scheme still favours the direct abstractor over the private source irrigator, though in both cases the cost of water bears little relation to its true value except for low-value crops such as grass. It is suggested that predictions for irrigation demand may be overestimated as a result of the charging scheme, though it is also contended that the Act does not provide sufficient guides to help the irrigator search for alternative means to improve crop yield. GEOGRAPHERS are showing an increasing interest in the means of allocating scarce resources, particularly in the case of conflicting multiple use of an important natural resource. Although this field has traditionally belonged to the engineer and economist, geographers are now realizing that they can make a significant contribution to the efficient management of resources (G. F. White, 1962; I. Burton and R. W. Kates, 1965; White, in prep.). A combined approach has reached its most sophisticated form in the field of water-resources management, particularly in the United States (National Academy of Sciences, National Research Council, 1966, 1968). One effect of this wider approach to the management of resources has been a change in the meaning of conservation. The old concept of preservation or protection from use has been replaced by a much more positive and dynamic attitude which emphasizes efficient multiplepurpose management. Each category of demand upon a scarce resource must be made as efficient as possible so that maximum benefits are derived with the minimum of wastage. To achieve this, each particular user is encouraged to consider various methods of utilization, each of which should provide the same benefits though utilizing the resource to different extents. This may lead to a change in the management of the resource, which, though it may involve additional private cost to the user, results in important social benefits. There are considerable advantages in evaluating the direct and indirect consequences of different uses of resources, both upon the individual and upon the community in space and time, and in relating the costs of the use of resources more directly to those who benefit. Examples include controlling development in flood hazard areas to reduce flood damage (Kates, 1962), improving effluent

Computers in Flood Control Planning

Federal agencies are required to seek the optimum combination of structural and nonstructural measures for flood control. Most procedures for systematic evaluation of all alternative combinations of structural and nonstructural measures are not feasible under current financial and manpower limitations. The only solution for complete evaluation is by means of the digital computer. Two flood control planning computer programs have been developed which select the optimum combination of channel improvement, flood proofing, and land use management by location within the flood plain and by time. The second program adds detention storage to the list of available alternatives. Both incorporate the entire plannning process from the raw data to a selected optimum program of measure use in one run. The programs have been applied to several flood hazard areas in California and Kentucky.