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The opening of the Bonnet Carré spillway to prevent flood threat to New Orleans in April 2008 created a sediment plume in the Lake Pontchartrain. The nutrient rich plume triggered a massive algal bloom in the lake. In this article, we have quantified the spatio-temporal distribution of the plume (suspended solids) and the bloom (chlorophyll-a (chl-a)) in the lake using remotely-sensed data. We processed the Moderate-resolution Imaging Spectroradiometer satellite data for mapping the total suspended solids (TSS) and chl-a concentrations. An existing algorithm was used for estimating TSS whereas a novel slope model was developed to predict the per-pixel chl-a concentration. Both algorithms were successful in capturing the spatio-temporal trend of TSS and chl-a concentrations, respectively. Algal growth was found to be inversely related to TSS concentrations and a time lag of ～45 days existed between the spillway opening and the appearance of the first algal bloom at an observation location. 相似文献
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1. THE GEOGRAPHICAL ENVIRONMENT AND HISTORICAL PERSPECTIVE OF THEPROJECTIn the western part of Sichuan Basin, between the Longmen Mountain in the west and theLongquan Mountain in the southeast, lies an alluvial plain of 6500 kmZ formed by the Minjiang Riversystem known as the Chengdu Plain. With its mild climate (average annual temperature 16' 4 C ),fertile soils, rich water resources, and the densely interconnected system of Minjiang and TuojiangRivers, Chengdu … 相似文献
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Ashok K. Chugh 《国际地质力学数值与分析法杂志》2007,31(4):607-648
A forced vibration procedure is presented to estimate fundamental and higher frequencies of vibrations and associated mode shapes of gravity structures. The gravity structures considered are retaining walls and gravity dams. The validity of the proposed procedure is tested on three test problems of varying complexity for which the natural vibration frequencies and mode shapes either have known analytical solutions or have been determined via numerical means/field tests by others. Also included are the results of natural vibration frequencies and associated mode shapes for a spillway control structure located near the abutment end of an embankment dam obtained using the proposed procedure. For all problems considered, fundamental frequency and mode shape results using the proposed procedure are compared with the results obtained using an alternative procedure in which static deflections due to the structure's own weight are used as the starting point for free vibrations by setting the gravity vector to zero. All results compare well. The merits of the proposed procedure are discussed. Published in 2006 by John Wiley & Sons, Ltd. 相似文献
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《国际泥沙研究》2000,(1)
lINTRoDUCTIONDamshavebeendesignedtraditionallynottobeovertoppedduringprobablemaximumfloodevents.AccordingtoPowledgeet.aI.(l989),manytensofthousandsofdamshave,however,becomepotentiallysubjecttoovertoppingasaresuItofimprovementsinthequalityofflooddataandinthemethodsfordeterminingprobablemaximumfloodsforwhichitisnotpossiblenoreconomicallyfeasibletoconsidermodificationstopreventovertopping.SomedamshavemoreoverbeenobservedtohavewithstoodmoderateoveFtopping.Effortshaveasaresultbeenconcentrated… 相似文献
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In this paper a new and efficient control method based on fuzzy logic is proposed for real‐time operation of spillway gates of a reservoir during any flood of any magnitude up to the probable maximum flood. Artificial neural networks are used to model the non‐linear relationship among the main variables of the reservoir under consideration. In order to demonstrate the performance of the proposed method, we simulate the control system using different probable overflow hydrographs. The results of the proposed control method are compared with the results of the conventional control methods. The results obtained from the simulations indicate that the proposed method exhibits superior performance over the conventional reservoir flood operation, with much more flexible results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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为进一步优化拦砂坝溢流口体型,确定溢流口几何参数取值,通过物理模拟实验研究了不同拦砂坝溢流口体型条件下泥石流过坝的流态、坝后冲刷深度、消能率变化规律,并根据拦砂坝埋深设计标准与松散体水下临界平衡关系,探讨了溢流口收缩率的合理取值范围,结果表明:采用斜面或者大倾角的反弧型溢流口时,坝后泥石流落点与坝脚的距离近、冲刷深度大,而采用无倾角的反弧型溢流面时,不仅可以在一定程度上减小冲刷深度,而且大大增加了坝后泥石流落点与坝脚的距离;在泥石流规模与溢流面曲率半径相同情况下,适当增大侧向收缩率,有利于增强泥石流体与坝后动床之间的相互作用,提高泥石流通过坝后冲刷坑的消能率;当溢流口收缩率在0.2~0.6之间时,冲刷深度满足设计要求,且泥石流跌落点距坝脚较远,冲刷坑发展不会危及坝体安全。 相似文献
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为更清楚地认识前置掺气坎阶梯溢洪道近壁面沿程掺气规律,对其掺气特性进行了研究,得到了在不同坡度、单宽流量、台阶体型条件下阶梯竖直面和水平面近壁处掺气浓度沿程分布规律,并与不设前置掺气坎但设置过渡阶梯溢洪道的掺气规律进行了对比分析。研究表明:前置掺气坎式阶梯溢洪道中阶梯水平面与竖直面掺气浓度沿程的分布规律相似,受前置掺气坎的帮助,掺气浓度很高,沿程逐渐减小,达到一定距离后趋于稳定;掺气浓度随单宽流量的增大而减小,随坡度的减缓而减小;前置掺气坎克服了过渡阶梯存在前几级的底部清水区的缺陷,能够用于更大单宽流量。 相似文献
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测压管——水库及大坝等水工建筑物的眼睛,用以观测地下水位、水温、水质等的动态变化规律。籍此资料可以测算渗透压力、温度应力以及水质对建筑物和基础的潜蚀或破坏的可能性,可以推测建筑物在使用过程中的稳定性。因而,它是一个非常重要的监测工具和手段。国内、外的水工建筑物几乎都埋设了测压管,并设有专门的机构对其进行长期观测。本文旨在利用北京密云水库第一溢洪道的测压管资料,来说明安全检查工作中发现的问题,即测压管水位偏高问题的研究方法和其对策。 相似文献
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