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Assessment of causal mechanisms on flood conveyance on the Tisza River, Hungary using one-dimensional retro- and scenario-modeling.

机译:使用一维逆向和情景模型评估匈牙利蒂萨河上洪水输送的因果机制。

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摘要

During the past decade, a series of record flood stages have occurred along the Tisza River, resulting in extensive damage and displacing the local floodplain population. Previous research on the Tisza River in Hungary showed increases in flood stages for fixed discharges (above bankfull). These results suggest that a loss of conveyance has taken place on the Tisza River, contributing to recent record flood levels.;In order to assess the potential causes of flood conveyance losses, new hydrological and geospatial data were obtained from the Hungarian Federal Hydrological Authority (VITUKI) in order to develop hydrodynamic models for two reference conditions, 1979 and 1999, along two study reaches on the Middle Tisza River. In addition to these models of actual conditions at each time step (i.e., "retro-models"), four "scenario models" were developed in order to test the individual impacts of each of the hypothesized causal mechanisms: 1) channel geometry, 2) levees, 3) floodplain roughness (land cover), and (4) channel roughness. Comparison of the models for actual conditions ("retro-model") and the scenario models allows for quantitative assessments of the impacts of each of these parameters on flood conveyance. In addition to these four scenario models, an additional land cover scenario-model was created to further assess the impact of floodplain roughness on stage.;Assessment of the two retro-models showed changes in flood stage along both study reaches over the 20-year time step. Along the upper study reach, changes in stage ranged between 0.64 and 1.64 m. On the lower study reach, changes in stage ranged from 0 to 1.75 m. These changes in stage were larger on average than changes in stage previously detected by Venzcel, 2008.;Contributions from the channel geometry scenario model were significant on the upper study reach where channel geometry decreased flood stage by up to 0.58 m at Kiskore over the 20-year time step. This was attributed to the dam that was constructed immediately upstream from the Kiskore gauge on the upper study reach. Construction of a dam would cause incision downstream, and therefore, a decrease in flood stage over time due to channel geometry. On the lower study reach, change in stage due to channel geometry was negligible.;Contributions from the levee scenario model were negligible on both the upper and lower study reach with a maximum change in stage over the 20-year time step at only 0.11 m. However, during the time step analyzed, no significant change in levee configuration occurred.;Changes in stage due to changes in land cover were also negligible along both study reaches. An additional land cover scenario model was created to assess the impact of land cover change on modern flood levels. This scenario model set Manning's n values for floodplain roughness to 0.04, which approximates roughness for pasture and cropland. This scenario model showed that flood stages will decrease by 0.34-0.40 m, but only if the entire floodplain is converted from woodland to pasture/cropland.;Channel roughness accounted for the majority of change in stage during the 20-year time step. Along the upper study reach, channel roughness accounted for an average of 1.51 m of change over the 20-year time step. On the lower study reach, channel roughness accounted for 1.03 m of change. Change in the stage/discharge relationship is the best explanation for changes in stage due to channel roughness. Most likely, the channel did not experience such a large change in roughness during the 20-year time step. Instead, the two flood years used in this analysis were different "types" of floods (with differing degrees of hysteresis), and the stage/discharge relationships could not be easily compared. Comparing these two floods may have exaggerated the total change in stage between the two retro-models. Backwater effects are a likely explanation for the change in hysteresis between the two flood years.
机译:在过去的十年中,蒂萨河沿岸发生了一系列创纪录的洪灾阶段,造成了广泛的破坏,并取代了当地的洪泛区人口。匈牙利对Tisza河的先前研究表明,固定排洪量(满水以上)的洪水期增加。这些结果表明,蒂萨河上发生了运输损失,造成了近期创纪录的洪水位。;为了评估洪水运输损失的潜在原因,从匈牙利联邦水文管理局获得了新的水文和地理空间数据(为了开发两个参考条件(1979年和1999年)的水动力模型,以及对蒂萨河中部的两次研究。除了在每个时间步长的这些实际情况模型(即“复古模型”)之外,还开发了四个“方案模型”以测试每种假设的因果机制的单独影响:1)通道几何形状,2 )堤防,3)洪泛区粗糙度(土地覆盖)和(4)河道粗糙度。通过比较实际情况模型(“复古模型”)和情景模型,可以定量评估每个参数对洪水输送的影响。除了这四个情景模型之外,还创建了一个额外的土地覆盖情景模型,以进一步评估洪泛区糙度对阶段的影响。两种逆向模型的评估显示,在这20年的研究期内,洪水阶段的变化时间步。沿上部研究范围,阶段变化范围为0.64至1.64 m。在较低的研究范围内,阶段变化范围为0至1.75 m。这些阶段变化平均要比Venzcel在2008年之前检测到的阶段变化大。;在上部研究范围内,通道几何情景模型的贡献非常显着,在20多个位置,Kiskore通道几何使洪水阶段最多减少了0.58 m。年时间步长。这归因于在研究上游河段Kiskore规上游直接建造的水坝。大坝的建设将在下游造成切口,因此,由于河道的几何形状,洪水期将随时间减少。在较低的研究范围内,由于通道几何形状引起的阶段变化可以忽略不计;;在较高和较低的研究范围内,堤防情景模型的贡献均可以忽略不计,在20年时间段内,最大的阶段变化仅为0.11 m 。然而,在所分析的时间步长中,堤防结构没有发生显着变化。在两个研究阶段,由于土地覆盖变化引起的阶段变化也可以忽略不计。创建了另一个土地覆盖情景模型,以评估土地覆盖变化对现代洪水位的影响。此场景模型将洪泛区粗糙度的Manning的n值设置为0.04,这近似于牧场和农田的粗糙度。该情景模型表明,洪水阶段将减少0.34-0.40 m,但前提是整个泛滥平原都从林地转变为牧场/农田。在20年的时间步长中,河道粗糙度占阶段变化的大部分。沿上部研究范围,河道粗糙度在20年的时间步长中平均产生1.51 m的变化。在较低的研究范围内,通道粗糙度占1.03 m的变化。阶段/放电关系的变化是对由于沟道粗糙度导致的阶段变化的最好解释。最有可能的是,在20年的时间步长中,通道的粗糙度没有发生如此大的变化。相反,此分析中使用的两个洪水年份是洪水的不同“类型”(具有不同的滞后程度),并且无法轻松比较水位/流量关系。比较这两次洪水可能会夸大这两个复古模型之间的阶段总变化。回水效应可能是两个洪水年份之间的磁滞变化的解释。

著录项

  • 作者

    Evanoff, Elizabeth.;

  • 作者单位

    Southern Illinois University at Carbondale.;

  • 授予单位 Southern Illinois University at Carbondale.;
  • 学科 Geology.;Geomorphology.
  • 学位 M.S.
  • 年度 2010
  • 页码 116 p.
  • 总页数 116
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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