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首页> 外文学位 >Remote sensing studies for the assessment of geohazards: Toxic algal blooms in the lower Great Lakes, and the land subsidence in the Nile Delta.
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Remote sensing studies for the assessment of geohazards: Toxic algal blooms in the lower Great Lakes, and the land subsidence in the Nile Delta.

机译：评估地质灾害的遥感研究：大湖下游的有毒藻华和尼罗河三角洲的地面沉降。

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Remote sensing techniques provide valuable tools for assessing a wide variety of environmental phenomena. They have been used for monitoring and assessment of various types of geologic and environmental hazards occurring on land, in the air, or in oceans. I present results from two studies, the first of which examines the spatial and temporal distribution of algal blooms in the Great Lakes; the second measures subsidence in the Nile Delta.;In the first study, methodologies to investigate the extent and distribution (temporally and spatially) of algal blooms in Lake Erie and Lake Ontario are studied. Millions of people in the U.S and Canada rely on the Great Lakes for drinking water, food, work, and recreation. Toxic algal blooms present a hazard to the substantial number of communities that draw water from the Great Lakes. Visible and infra red MODIS satellite data are used to map the extent of algal blooms in these lakes. Existing algorithms to retrieve chlorophyll concentrations are successfully tested against in situ measurements from sampling cruises. Algorithms are developed to identify the potentially toxic cyanobacterial blooms.;The second study examines subsidence in the Nile Delta. The modern Nile Delta is the major agricultural production area for Egypt and was formed from sediments supplied by at least 10 distinct distributary channels throughout the Holocene. With an average elevation around a meter above sea level and with a predicted rise in sea level of 1.8--5.9 mm/year the subsidence of the northern 30 km of the delta is a topic of major concern to the Egyptian population and government. Ongoing subsidence rates in the northeastern Nile Delta were estimated using persistent scatterer radar interferometry techniques. The highest rates (∼8 mm/yr; twice average Holocene rates) correlate with the distribution of the youngest deposition, with older depositional centers subsiding at slower rates of 2--6 mm/yr. Results are interpreted to indicate that: (1) modern subsidence in the Delta is heavily influenced by the compaction of the most recent sediments, and (2) the highly threatened areas are at the terminus of the Damietta, where the most recent deposition has occurred.
机译：遥感技术为评估各种环境现象提供了有价值的工具。它们已用于监视和评估在陆地，空中或海洋中发生的各种地质​​和环境危害。我提供了两项研究的结果，第一项研究了五大湖中藻华的时空分布。在第一项研究中，研究了调查伊利湖和安大略湖中藻华的程度和分布的方法（时空分布）。美国和加拿大有数百万人依靠五大湖来获得饮用水，食物，工作和娱乐。有毒藻华对大量从大湖汲水的社区构成危害。可见和红外的MODIS卫星数据用于绘制这些湖泊中藻华的程度。现有的检索叶绿素浓度的算法已针对抽样巡视中的现场测量结果成功进行了测试。开发了识别潜在毒性蓝藻水华的算法。第二项研究研究了尼罗河三角洲的沉降。现代化的尼罗河三角洲是埃及的主要农业产区，由全新世至少10条不同的分布河道提供的沉积物形成。埃及三角洲北部30公里处的平均沉降高度约为海平面以上一米，预计海平面每年将上升1.8--5.9毫米，这是埃及人口和政府最关心的话题。使用持续散射雷达干涉测量技术估算了东北尼罗河三角洲的持续沉降率。最高的沉积速率（约8毫米/年；平均全新世速率的两倍）与最年轻的沉积物的分布有关，而较老的沉积中心则以2--6毫米/年的较慢速率沉降。结果解释为：（1）三角洲的现代沉降受到最新沉积物压实的严重影响；（2）受威胁最大的地区位于达米埃塔（Damietta）的末端，最近的沉积发生。

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