我国水灾与可持续发展研究

根据我国水灾的有关资料 ,研究了我国水灾的基本特点 ,分析了水灾形成的主要原因及其对可持续发展的制约作用 ,提出了根治水灾必须走可持续发展的道路     

THE IMPACT OF FLOODPLAIN REGULATIONS ON RESIDENTIAL LAND VALUES IN OREGON1

ABSTRACT: The impact of floodplain regulations on mean appreciation rates of residential land values was tested at six study areas in five counties in western Oregon. The study hypothesis that such regulations significantly depress appreciation rates of regulated lands relative to those of similar unregulated lands was in most cases rejected. When the hypothesis was accepted circumstances would render conclusions tenuous. The problems and issues facing this type of research are presented in case studies of two of the research study areas. The following factors challenge investigators seeking to resolve questions about the relationship between land use regulations and land values: varying degrees of stringency with which regulations are enforced; unequal assessment procedures between counties; influences external to floodplain regulations that may affect appreciation rates, including denial of permits for septic tanks, flood damages, and amenity values associated with waterfront locations; and the uncertain effect that the availability of flood insurance, which accompanies floodplain regulations, has on land values.     

SOME TECHNIQUES FOR USING FREQUENCY ANALYSIS AND REALTIME DATA TO INTERPRET FLOOD POTENTIAL DATA1

ABSTRACT: Flood potential data can be effectively interpreted if simple frequency analysis concepts are used to explain the significance of flood potential. Instead of simply presenting data as a quantitative amount or as a percentage of the average condition, predictions can be discussed in terms of their probabilities of exceedance, or return periods. Criteria are presented for evaluating the significance of various return periods. Frequency interpretations are applied to snow course data, peak flow forecasts, and streamflow volume forecasts in northern Utah to illustrate these concepts. In addition, access to realtime data allows tracking of snowmelt progression and identification of any deviations from the forecast flood potential situation. Several data elements, including snowpack, streamfiow volume and peak, and realtime data are jointly evaluated to assess potential hazard and probable risk.     

CORRELATION OF ANNUAL PEAK FLOWS FOR PENNSYLVANIA STREAMS1

A common assumption in flood frequency analysis is that annual peak flows are independent events. This study was undertaken to investigate the validity of this assumption with regard to Pennsylvania streams by statistically analyzing the dependence between annual peak flows and to determine if basin carryover effects relate to the degree of dependence. Five tests of dependence, the autocorrelation test, the median crossing test, the turning points test, the rank difference test, and the Spearman rank order serial correlation coefficient test were applied to the series of annual peak flows for 57 streams. Of the 57 streams analyzed, only two exhibited signs of dependence by at least two of the tests performed, and the baseflow component of annual peak flows was found to be unrelated to the degree of dependence exhibited between annual peak flows. It was concluded that the assumption of independence of annual peak flows is valid in flood frequency analysis for Pennsylvania streams.     

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.     

UNIVARLATE LEAST SQUARES MUSKINGUM FLOOD ROUTING1

ABSTRACT: The Muskingum method of hydrologic flood routing is based on a graphical bivariate curve fitting procedure. The subjectivity of this procedure may lead to problems of reproducibility and provides no guarantee of model coefficients which minimize the error of estimation. A transformation is developed to express the Muskingum method as a univariate transcendental function suitable for numeric solution. Solution of this function minimizes the sum of the squared deviations between estimated and measured rates of discharge. Five textbook examples of the Muskingum method are evaluated by the univariate transformation. Error reductions range from negligible to tenfold. While the univariate transformation may not improve upon graphically-based results in every case, in no instances are the univariate results inferior; in many cases they are superior.     

REGIONALIZATION AND PREDICTION OF FLOODS IN THE FRASER RIVER CATCHMENT,B.C.1

Probability distributions that model the return periods of flood characteristics derived from partial duration series are proposed and tested in the Fraser River catchment of British Columbia. Theoretical distributions describing the magnitude, duration, frequency and timing of floods are found to provide a goof fit to the observed data. The five estimated parameters summarizing the flood characteristics of each basin are entered into a discriminant analysis procedure to establish flood regions. Three regions were identified, each displaying flood behavior closely related to the physical conditions of the catchment. Within each region, regression equations are obtained between parameter values and basin climatic and physiographic variables. These equations provide a satisfactory prediction of flood parameters and this allows the estimation of a comprehensive set of flood characteristics for areas with sparse hydrologic information.     

AN EVALUATION OF FLOOD FREQUENCY ESTIMATES BASED ON RAINFALL/RUNOFF MODELING1

ABSTRACT: An evaluation of flood frequency estimates simulated from a rainfall/runoff model is based on (1) computation of the equivalent years of record for regional estimating equations based on 50 small stream sites in Oklahoma and (2) computation of the bias for synthetic flood estimates as compared to observed estimates at 97 small stream sites with at least 20 years of record in eight eastern states. Because of the high intercorrelation of synthetic flood estimates between watersheds, little or no regional (spatial) information may be added to the network as a result of the modeling activity. The equivalent years of record for the regional estimating equations based totally on synthetic flood discharges is shown to be considerably less than the length of rainfall record used to simulate the runoff. Furthermore, the flood estimates from the rainfall/runoff model consistently underestimate the flood discharges based on observed record, particularly for the larger floods. Depending on the way bias is computed, the synthetic estimate of the 100-year flood discharge varies from 11 to 29 percent less than the value based on observed record. In addition, the correlation between observed and synthetic flood frequency estimates at the same site is also investigated. The degree of correlation between these estimates appears to vary with recurrence interval. Unless the correlation between these two estimates is known, it is not possible to compute a weighted estimate with minimum variance.     

Reduction of Urban Runoff Through Economic Incentives: Boulder,Colorado1

ABSTRACT: The problems of increased surface runoff which follow in step with urbanization can be conceptualized in terms of environmental economics. The private transformation of land from a permeable to an impermeable surface imposes the externality of increased surface runoff upon society as a whole and especially on those downstream. The city of Boulder, Colorado, has enacted an ordinance which attempts to internalize some of these external costs and at the same time decrease surface runoff from the urban environment.     

LEGAL CHALLENGE OF THE UNGAGED WATERSHED1

The lack of uniform techniques for estimating design discharges in ungaged areas is a source of growing concern in the courts now faced with challenges to floodplain boundaries and culvert design for highway crossings. This paper summarizes a court case in which calculations of the design discharge and the hydraulic backwater effects of a major highway culvert were contested by the plaintiff. Emphasis in the paper is placed on the variation in computed flows and the interpretation of the court in the face of diverse hydrologic methods for the ungaged watershed. The results of a preliminary evaluation of ungaged watershed methods applicable to Pennsylvania are also reported in terms of standard error and bias.