EMERGING STATE ROLES IN URBAN STORMWATER MANAGEMENT1

ABSTRACT: The technology of urban stormwater management has far outpaced its actual application in new urban development. This article documents that implementation gap, but shows that state and local governmental measures, particularly storm drainage regulations, can lead to improved performance in the private sector. Although state stormwater management programs are in their infancy, they are already having a measurable effect in stimulating the adoption of local governmental programs to manage urban storm water. Pioneering state programs in Maryland, New Jersey, and Pennsylvania, described in this article, provide models for states contemplating the formulation of stormwater management programs.     

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.     

FLOODPLAIN STORAGE AND LAND USE ANALYSIS AT THE WOODLANDS,TEXAS1

ABSTRACT: The Woodlands, a totally planned community north of Houston, Texas, was studied in detail in an effort to develop a master drainage plan which minimizes adverse impact on the 100-year floodplain. A total of 40 HEC-1 and HEC-2 computer runs were made to evaluate various development, channelization, and reservoir storage options.     

THE HYDROLOGIC ENGINEERING CENTER EXPERIENCE IN NONSTRUCTURAL PLANNING1

ABSTRACT: The Hydrologic Engineering Center, Corps of Engineers, has been engaged in research, training, and project assistance in non-structural flood control planning for Corps offices across the United States since 1975. Lessons learned from this experience deal with the role of nonstructural measures in flood plain management, the role of creativity in analysis, the role of analysis, and tools for analysis. The role of nonstructural measures in flood control planning depends upon the scale of the problem, the nature of the measure, the degree of protection desired, and whether damage is to existing or future property. An earnest seeking for nonstructural opportunities, a field presence for their formulation, and compatbility with local infrastructure plans are prerequisite to creative use of nonstructural measures. Analysis is a necessary complement of creativity. Several tools for nonstructural analysis have been developed and applied to flood problems involving several hundred and several thousand structures.     

FLOOD PLAIN MODELING1

Computer simulation of river basin hydrology has rapidly progressed from an interesting academic exercise to a practical engineering procedure of increasing utility. Mathematical models of the many interrelated processes which occur in a basin have been developed along with efficient numerical procedures for their solution. The present paper is concerned with a particular model which has been used to describe the transformation of a temporally and spatially varying rainfall into a time history of stage and discharge on a flood plain. Although developed principally as a model of the physical processes involved, it is envisioned that the model can serve as one component of an information system for flood plain planning and management. The model consists of the following elements: (i) a rainfall simulation which generates stochastic inputs to the model according to specified rainfall statistics, (ii) a catchment-runoff model which converts the rainfall to surface runoff, (iii) a flood stage model which converts the surface runoff to time histories of flood stage and discharge. The model has been used to investigate the effect of various structural flood control measures in a basin and, in particular, to establish frequency-stage information for each of these. Of particular interest in development of the model have been recurring and partially unanswered questions relative to the proper balance among availability of data for use in the model, data requirements of the model and the objectives of the outputs produced by the model.     

FLOOD INUNDATION IN THE SOUTHEASTERN UNITED STATES FROM AIRCRAFT AND SATELLITE IMAGERY1

ABSTRACT: Panchromatic black and white, color, and color infrared photographs and thermal infrared imagery are compared for a capability to show flood boundaries. In open agricultural and urban areas, these boundaries are easily delineated on all types of am. Boundaries are more difficult to see in wooded areas. In March, hardwood trees are dormant, but black and white photographs and color photographs show only the tops of these trees. Color infrared photographs in January and March have a distinctive color or tone in inundated woods; the limit of this tone is the flood boundary. Daytime thermal infrared imagery in March shows that inundated woods are cooler than dry land but warmer than open water. After about April 1, both color infrared photography and thermal infrared imagery show only the top of the tree canopy and do not reflect underlying flood water. Inundated areas can be delineated easily on ERTS satellite imagery from December through March. On imagery from May 4–5, 1973, however, most inundation boundaries had to be drawn as dashed lines; the tree canopy obscures flood waters in wooded areas. Despite this problem, the results of mapping flood boundaries on May imagery are believed to be reasonable for the scale of the imagery.     

THE MEASUREMENT OF IMPACTS IN SMALL WATERSHEDS FOR FLOOD CONTROL1

ABSTRACT: An analogue method of ex post evaluation is proposed as a method of measuring the effectiveness of small watershed projects in obtaining flood control and economic benefits. Two watersheds were compared on a “with vs. without” project basis by both direct and indirect measurement of economic benefits. Direct measurements indicated that small watershed flood control projects did not generate the expected economic benefits. However, the indirect measurements of the same watersheds using land value enhancement as a surrogate suggested that the expected economic benefits were reflected in differential land values. The economic efficiency of small watershed projects should be measured ex ante and ex post on a “with vs. without” project basis rather than on a “before vs. after” basis whether using direct or surrogate variables.     

闽北地区“6.22”特大山体滑坡及其治理对策

１９９８年６月２２日,闽北地区出现百年一遇的特大洪水,从而引发了政和县境里发生特大山体滑坡。本文就此次灾害的灾情、发生条件进行了分析;并对如何识别地质灾害及如何防治滑坡灾害作了进一步分析。     

1995年气候对交通系统的影响

根据气象部门和交通部门的资料，对１９９５年气候条件对我国交通系统造成的影响进行了分析评述，其中影响最大的是暴雨洪水，其它气候灾害还有雾、雪、风及高温等，使我们对影响交通系统的气候灾害有了进一步的认识。     

REGION OF INFLUENCE REGRESSION FOR ESTIMATING THE 50-YEAR FLOOD AT UNGAGED SITES1

ABSTRACT: Five methods of developing regional regression models to estimate flood characteristics at ungaged sites in Arkansas are examined. The methods differ in the manner in which the State is divided into subregions. Each successive method (A to E) is computationally more complex than the previous method. Method A makes no subdivision. Methods B and C define two and four geographic subregions, respectively. Method D uses cluster/discriminant analysis to define subregions on the basis of similarities in watershed characteristics. Method E, the new region of influence method, defines a unique subregion for each ungaged site. Split-sample results indicate that, in terms of root-mean-square error, method E (38 percent error) is best. Methods C and D (42 and 41 percent error) were in a virtual tie for second, and methods B (44 percent error) and A (49 percent error) were fourth and fifth best.