@inproceedings{oai:kitami-it.repo.nii.ac.jp:00007843, author = {吉川, 泰弘 and 渡邊, 康玄 and YOSHIKAWA, Yasuhiro and WATANABE, Yasuharu}, book = {北海道開発土木研究所月報}, month = {Sep}, note = {物質(SS および栄養塩類) の輸送は主に出水時に多く行われる。また、栄養塩類は生態系に影響を与えるため、その挙動の把握は河川環境を維持および管理する上で重要である。本研究の目的は大きく分けて2 つあり、大規模洪水が物質輸送に与える影響を把握する事、洪水規模による河道内への影響の違いを把握するために、洪水後に堆積するSS および栄養塩類量を推算する事である。対象流域を沙流川として研究を3 つの手順で進めている。1 つ目は、洪水と融雪出水を含む4 出水における物質輸送の相違の把握を目的に観測データを精査した。2 つ目は、洪水による高水敷への栄養塩類堆積量を推算するために観測データから推定式を導出した。3 つ目は、洪水規模の違いによる高水敷へのSS および栄養塩類堆積量の相違を明らかにするために計算を行った。結果として、1 つ目は河道内からの物質供給量は流量と関連があり、ある一定の流量を超えると流水中の物質が飽和濃度に達すると推測された。また、大規模出水後の融雪出水において流量に対する物質の濃度が上昇する事が分かった。2 つ目は栄養塩類推定式を導出しシルトと粒子性水質成分との相関が良いことが分かった。3 つ目は洪水規模の違いにより河川環境へ与える影響は場所的に異なる事が計算により分かった。, Transport of Materials ( suspended solids (SS) and nutrient salt ) increases during floods. Nutrient salts transported in river water are important in terms of river ecosystems. Understanding of nutrient salt behavior in the river environment is important in the maintenance and management of the rivers. To better understand the influence of flooding on the river environment, this study aims to clarify the influence that a large-scale flood gives to the material transportation, and to estimate the amount of SS and nutrient salts deposited on the flood plain as a result of flood. The study area was the Saru River basin, and the study was conducted in three steps. First, toward understanding the differences in material transport in four floods (two rainfall floods and two snowmelt floods) observation data were examined. Second, equations were derived from the observation data in order to estimate the amounts of SS and nutrient salts deposited on the flood plain as a result of flooding events. Third, calculation for unsteady flow in a compound cross-section was performed to clarify how the amounts of nutrient salts deposited in the high-water channel differ by the flood scale. The following were found: 1) The volume of material supplied from the channel relates to the discharge, and we could hypothesize that when the discharge reaches a certain threshold, the material being transported reaches a saturation concentration. Moreover, in the snowmelt flood before and behind the Large-scale flood, the thing that the density of the material in the stream rises has been understood. 2) From the estimation equation that we derived for nutrient salts, we found a close correlation between the amount of silt deposition and the amount of water quality components in particulate form. 3) The calculations revealed that the influence of floods of different scale on the river environment varies by location.}, pages = {2--17}, publisher = {国土交通省北海道開発局土木研究所}, title = {物質輸送に与える大規模洪水の影響}, volume = {628}, year = {2005} }