SUMMER FLOODING AT CHICAGO AND POSSIBLE RELATIONSHIPS TO URBAN-INCREASED HEAVY RAINFALL1

ABSTRACT: : Studies of two measures of flooding in the Chicago metropolitan area reveal a wide range of floods with the magnitude related to recurrence interval expressions of rain intensity. Minor type floods (in basements and underpasses) usually result from localized heavy rains (≤ 3-hour duration) with return intervals of 1 to 2 years, and more major floods result from rains with return intervals of 2 to 5 years (or more). Urban-factors help lead to increases in warm season rain events in Chicago with 1- to 4-year return intervals. These apparently help lead to 10 to 100 percent more flooding events in Chicago than expected. The range of increase varies depending on locale and type of flood, but the increases in storms should be accounted for in drainage designs.     

THE RED RIVER FLOOD CONTROL SYSTEM AND RECENT FLOOD EVENTS1

ABSTRACT: The 1950 flood disaster in the Red River Valley, Manitoba, and particularly in Winnipeg made all levels of government aware of the need for control measures. The principal elements of the system which was implemented were two large excavated diversion channels, a storage reservoir, and ring dykes around several small communities. In terms of cost and size, the flood control system is the largest in Canada and despite Federal contributions amounting to nearly 60 percent of the final cost, it represented a considerable fiscal burden for the comparatively small population of Manitoba. Between the opening of the Red River Floodway in 1968 and 1979, a series of exceptional spring peak flows on the Red and Assiniboine Rivers demonstrated the benefits of such a system to a degree which could not have been anticipated at the time the projects were being considered. Furthermore, maximum spring discharges from 1913 to 1978 show a clear rising trend, indicating that the flood hazard is becoming even more severe than was initially assumed; if this trend continues, future benefits will continue to exceed expectations. The overall effectiveness of the hazard reduction program in the Red River Valley, however, has suffered from continued development in unprotected areas. Recent federal-provincial agreements have been reached which will substantially reduce this problem and place greater emphasis on improving the non-structural components of an overall flood hazard reduction program.     

有毒液体泄漏渗流污染后果分析

有毒液体泄漏后,沿地表扩散的同时亦会发生渗流现象.有毒液体渗流会直接或间接地对土壤和地下水及周边环境造成一定的污染,甚至会对人体造成很大危害,导致中毒等重大事故的发生.为分析泄漏后毒物的浓度在时间和空间上的变化规律,建立了二维渗流方程,开发了二维渗流事故后果分析软件.分析结果表明,在假设前提下,毒物泄漏后发生渗流时,毒物浓度沿二维渗流平面呈椭圆形向四周扩散,泄漏点的浓度随泄漏时间的推移而逐渐降低,此结论对于有毒液体泄漏的预防与控制具有重要的意义.     

北京市冬季PM_(2.5)污染特征与区域传输影响研究

选取北京师范大学监测点于2015年1月进行PM_(2.5)样品采集,应用离子色谱仪(IC)分析PM_(2.5)中水溶性无机离子质量浓度,采用WRF-CAMx-PSAT模型系统对采样时段PM_(2.5)及典型离子的区域来源进行了模拟。结果表明,采样期间(2015年1月2—20日)与重污染过程(2015年1月13—15日)北京PM_(2.5)质量浓度分别为(105.9±72.6)μg/m~3和(232.2±80.2)μg/m~3,PM_(2.5)中总水溶性无机离子质量浓度分别为(47.4±39.8)μg/m~3和(120.7±23.3)μg/m~3,分别占PM_(2.5)的44.2%和53.9%。SO_4~(2-)、NO_3~-和NH_4~+是水溶性离子的主要组分,非重污染过程和重污染过程这3种水溶性离子质量浓度之和分别占总水溶性离子质量浓度的80.5%和89.3%。模拟结果显示,本地源排放是北京市PM_(2.5)、SO_4~(2-)、NO_3~-、NH_4~+的主要来源,贡献率分别为81.4%、79.5%、58.1%、95.3%,北京周边源排放对PM_(2.5)贡献率较大的有保定、天津、张家口、唐山,这4市占北京周边省市排放源贡献率的72.0%。     

GENERALIZED SKEW COEFFICIENTS FOR FLOOD FREQUENCY ANALYSIS1

ABSTRACT: In order to promote a uniform and consistent approach for floodflow frequency studies, the U.S. Water Resources Council has recommended the use of the log-Pearson type III distribution with a generalized skew coefficient. This paper investigates various methods of determining generalized skew coefficients. A new method is introduced that determines generalized skew coefficients using a weighting procedure based upon the variance of regional (map) skew coefficients and the variance of sample skew coefficients. The variance of skew derived from sample data is determined using either of two non-parametric methods called the jackknife or bootstrap. Applications of the new weighting procedure are presented along with an experimental study to test various weighting procedures to derive generalized skew coefficients.     

ASPEN CLEARCUTTING INCREASES SNOWMELT AND STORM FLOW PEAKS IN NORTH CENTRAL MINNESOTA1

ABSTRACT: Clearcutting aspen from the upland portion of an upland peatland watershed in north central Minnesota caused snowmelt peak discharge to increase 11 to 143 percent. Rainfall peak discharge size increased as much as 250 percent during the first two years after clearcutting, then decreased toward precutting levels in subsequent years. Storm flow volumes from rain during the first two years increased as much as 170 percent but declined to preharvest volumes in the third year. Snowmelt volumes did not significantly change. Snowmelt peak discharge occurred about four to five days earlier after clearcutting, but the timing of storm flow from rainfall was not changed. Snowmelt peaks remained above precut size for nine years after clearcutting on an area undergoing natural regeneration to aspen saplings. Partial cutting - up to approximately one-half of the watershed - reduced peak snowmelt discharge because melt was desynchronized in cleared and forested parts. Clearing more than 2/3 of the watershed caused snowmelt flood peak size to double during years with snow packs in excess of seven inches of water that remained until a day when maximum air temperatures exceeded 60d?F.     

南海海洋环境下关键电器设备腐蚀环境净化技术研究

南海海洋大气环境下,电器设备腐蚀问题形势非常严峻,严重影响生产任务和财产安全,非常有必要对电器设备采取有效的防护措施。开展了电器设备服役微环境腐蚀严酷度量化表征方法研究以及南海海洋环境下电器设备腐蚀环境净化技术研究,采用适当的腐蚀环境净化技术为关键电器设备内部提供洁净的空气,从而实现对电器设备的有效保护。     

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.