Recovery of Riverbed Features and Invertebrate Community in Degraded Channels by Sediment Supply through Bypass Tunnel

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Distributions of biogeochemical parameters in the pool and interstitial waters in sand bar system of the Kizu River

Distributions of biogeochemical parameters in temporary pools (TAMARI), riparian side arm of river (WANDO) and interstitial waters were investigated in the sand bars along the lower reaches of the Kizu River. Dissloved inorganic nitrogen (DIN) and phosphate (DIP) concentrations in TAMARI and WANDO waters varied greatly compared with those in river waters. Low concentrations of DIN and DIP were often observed simultaneously in TAMARI waters. The DIN concentrations of most intersitial waters were similar or high in comparison to those of river waters. Low concentrations of DIN and DIP were often observed separately in intersitial waters. Concentrations of biogeochemical constituents clearly varied greatly in the waters of sand bar systems, and the relationships between each biogeochemical constituents were different between surface water (TAMARI and WANDO) and subsurface (intersitial) waters of the Kizu River.Article信州大学山地水環境教育研究センター研究報告 2: 63-67(2004)departmental bulletin pape

Short-term influences of flow alteration on microbial community structure and putative metabolic functions in gravel bar hyporheic zones

Microbial communities in the hyporheic zone are important for self-purification as the riverbed is metabolically active and responsible for the retention, storage, and mineralisation of organic matter transported in the surface water. Studies exploring the response of the hyporheic microbial community to flow regime alterations remain scarce. Here, we characterised the microbial community structure over downwelling, upwelling and intermediate hyporheic zone areas within and among gravel bars at high and low discharge levels to determine flow-induced changes in a dam-regulated river using 16S rRNA gene sequencing. At low discharge, microbial composition varied across the different areas of gravel bars, reflecting heterogeneity in local abiotic conditions. However, high discharge lead to microbial community homogenisation across the three areas of the gravel bars. Microbial communities across adjacent gravel bars remained dissimilar regardless of discharge levels, likely reflecting differences in bar morphology. Our results can help better understand how anthropogenic changes in hydrologic conditions can affect microbial diversity and function in the hyporheic zone. This knowledge will help us to understand better how changes in hydrological conditions affect ecosystem functions and services in rivers affected by human impacts

ナミヒラタカゲロウの繁殖生態

京都大学0048新制・課程博士理学博士甲第4597号理博第1278号新制||理||708(附属図書館)UT51-90-L5京都大学大学院理学研究科動物学専攻(主査)教授 川那部 浩哉, 教授 日高 敏隆, 教授 手塚 泰彦学位規則第5条第1項該当Kyoto UniversityDFA

Evaluation of Cross-sectional Geomorphology for Lentic Habitat Restoration in the Uji River

Most of rivers in civilized countries have lost biodiversity due to deterioration of habitats by the artificial river works such as channelization, sand mining and dam construction. The Uji River is a typical river suffered by degradation and bipolazation of the riverbed due to reduced sediment dynamism and step-wise flow regime caused by the gate operation at Seta Barrage for control the discharge from the Lake Biwa, leading to decreased the connectivity of the main channel and the bank side lentic habitats. In this paper, we analyzed relations of aquatic animal communities in lentic habitats to the riverbed geomorphological parameters such as relative height of the habitat to the main channel, the length of cross-sectional perimeter, floodplain vertical shape index (FVSI), and clay layer distribution. Based on the results, the lentic habitats were classified into three types: 1) Low relative height ponds with high biodiversity with taxonomic groups common with lotic habitats, 2) terrace ponds with intermediate and high relative height with low biodiversity with taxonomic groups common with moor-like still water habitats, 3) island bar ponds with high relative height with rather high biodiversity. In addition, we found that the location of these lentic habitats showed a fairly good correspondence to the clay layer distribution. Based on these interrelationships, we proposed a method for evaluation of lentic habitat potential combining a suitable relative height with the underground clay layer distribution. This method will be applicable to nature restoration plans for creation of lentic habitats in degraded rivers in general as well as in the Uji River

タリアメント川 網状河道における粒状有機物の捕捉過程に関する研究

タリアメント川における原生的洪水氾濫源の豊かな生物多様性を維持する一つの原因である, 網状河道砂州の粒状有機物の捕捉機能を定性的, 定量的に研究した。運河, 単断面河道, 網状河道などの調査地点で流下粒状有機物の濃度, 炭素-窒素の安定同位体比, CN比及び付着藻類のクロロフィルa値を分析した結果, 運河では粒状有機物の移動機能, 単断面河道では隣の陸地域からの供給機能, そして網状河道の砂州では捕捉機能が支配的であることが明確に示された。 また, 二次流の流速と流向が砂州地形の捕捉過程において重要であることが示された。Channel geomorphology has ecologically important functions to remove organic particles from flowing water providing availability of organic matter to benthic organisms. The present study focuses on the roles of braided gravel-bar for riverine organic matter retention, aiming to elucidating the retention processes corresponding to the diverse hydrogeomorphological conditions in the Tagliamento River in north east Italy. Results of longitudinal changes in concentration, stable isotope analyses and C:N ratio of suspended particulate organic matter (POM) as well as in chlorophyll a of epilithon, which were collected at canal, narrow channel and braded bars, showed a distinct retention pattern and algal production of braided-bar. In addition, we found that secondary flow velocity and direction occurred near bar shoreline can be critical factors to affecting suspended POM retention. On the other hand, in an island bar unit, barhead riffle and bartail shore showed a selective retention capacity according to particle size. Overall the spatial diversity of POM quantity and quality along gravel-bar can lead to high heterogeneous habitats in braided channel.タリアメント川における原生的洪水氾濫源の豊かな生物多様性を維持する一つの原因である, 網状河道砂州の粒状有機物の捕捉機能を定性的, 定量的に研究した。運河, 単断面河道, 網状河道などの調査地点で流下粒状有機物の濃度, 炭素-窒素の安定同位体比, CN比及び付着藻類のクロロフィルa値を分析した結果, 運河では粒状有機物の移動機能, 単断面河道では隣の陸地域からの供給機能, そして網状河道の砂州では捕捉機能が支配的であることが明確に示された。 また, 二次流の流速と流向が砂州地形の捕捉過程において重要であることが示された。Channel geomorphology has ecologically important functions to remove organic particles from flowing water providing availability of organic matter to benthic organisms. The present study focuses on the roles of braided gravel-bar for riverine organic matter retention, aiming to elucidating the retention processes corresponding to the diverse hydrogeomorphological conditions in the Tagliamento River in north east Italy. Results of longitudinal changes in concentration, stable isotope analyses and C:N ratio of suspended particulate organic matter (POM) as well as in chlorophyll a of epilithon, which were collected at canal, narrow channel and braded bars, showed a distinct retention pattern and algal production of braided-bar. In addition, we found that secondary flow velocity and direction occurred near bar shoreline can be critical factors to affecting suspended POM retention. On the other hand, in an island bar unit, barhead riffle and bartail shore showed a selective retention capacity according to particle size. Overall the spatial diversity of POM quantity and quality along gravel-bar can lead to high heterogeneous habitats in braided channel

源頭渓流において土石流が河道内土砂と生息場構造に及ぼす影響

奈良県十津川村の人工林施業域において、土石流発生履歴の異なる42の源頭渓流を対象に、河道内土砂量、ハビタット要素の多さ、ミクロハビタット構造を調査した。土石流発生履歴と河道内土砂の関係は見られなかったが、土石流によって倒木、落葉枝ダムや堆積卓越型ミクロハビタットが減少することを明らかにした。底生動物群集を規定するミクロハビタットの多様性は土石流発生の履歴とともに変動することを示した。Disturbance plays key roles maintaining species diversity and ecosystem function in wide range of ecosystems. We examined relationships between debris flow history and stream habitat structure (in-channel sediment deposits, abundance of streambed elements, occurrence of different types of microhabitats) using 42 headwater streams with different histories of debris flows in a managed forest watershed, Totsukawa, Nara. In-channel sediment deposit was highly correlated with channel slope and valley width, and related little to debris flow history. Number of large woody pieces and woody debris dams were more in streams with older occurrence of debris flow. Erosive microhabitats such as bedrock, splash zone, moss mat were common in all streams, while depositional microhabitats such as mud and leaf pack occurred only in streams with old (>30 yrs) debris flow, and sand was absent in streams with very old (>50 yrs) debris flow. These results indicate that stream habitat diversity is dynamically maintained in a repeated manner through debris flow history.奈良県十津川村の人工林施業域において、土石流発生履歴の異なる42の源頭渓流を対象に、河道内土砂量、ハビタット要素の多さ、ミクロハビタット構造を調査した。土石流発生履歴と河道内土砂の関係は見られなかったが、土石流によって倒木、落葉枝ダムや堆積卓越型ミクロハビタットが減少することを明らかにした。底生動物群集を規定するミクロハビタットの多様性は土石流発生の履歴とともに変動することを示した。Disturbance plays key roles maintaining species diversity and ecosystem function in wide range of ecosystems. We examined relationships between debris flow history and stream habitat structure (in-channel sediment deposits, abundance of streambed elements, occurrence of different types of microhabitats) using 42 headwater streams with different histories of debris flows in a managed forest watershed, Totsukawa, Nara. In-channel sediment deposit was highly correlated with channel slope and valley width, and related little to debris flow history. Number of large woody pieces and woody debris dams were more in streams with older occurrence of debris flow. Erosive microhabitats such as bedrock, splash zone, moss mat were common in all streams, while depositional microhabitats such as mud and leaf pack occurred only in streams with old (>30 yrs) debris flow, and sand was absent in streams with very old (>50 yrs) debris flow. These results indicate that stream habitat diversity is dynamically maintained in a repeated manner through debris flow history

Riverbed Management by Changing Reach Scale Channel Configuration

Many rivers experienced channel alternation, riverbed degradation and vegetation expansion result from artificial disturbance. Thus, works of channel reconstruction carried out as a river restoration such as channel widening, excavation or making meandering. This study presents possibility of channel widening by changing reach scale channel configuration (RSCC). RSCC and their historical changes in the Kizu River during 1961 and 2010 were plotted in biplot dimension of width/depth ratio and specific stream power. And based on their historical changes, we predict resultant RSCC after manipulation of channel width. According to results, most of recent channel types were distributed in the range of low width/depth ratio. However, channel widening about 1.8-2.0 times in upper and lower site could be changed to the range of high width/depth ratio having high potentials of biodiversity in the Kizu River.Many rivers experienced channel alternation, riverbed degradation and vegetation expansion result from artificial disturbance. Thus, works of channel reconstruction carried out as a river restoration such as channel widening, excavation or making meandering. This study presents possibility of channel widening by changing reach scale channel configuration (RSCC). RSCC and their historical changes in the Kizu River during 1961 and 2010 were plotted in biplot dimension of width/depth ratio and specific stream power. And based on their historical changes, we predict resultant RSCC after manipulation of channel width. According to results, most of recent channel types were distributed in the range of low width/depth ratio. However, channel widening about 1.8-2.0 times in upper and lower site could be changed to the range of high width/depth ratio having high potentials of biodiversity in the Kizu River