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This article focuses on how ecosystem-based approaches could be mainstreamed in recovery and reconstruction after large scale, rare and infrequent coastal hazards. In doing so, this study reviews historical practices of disaster management in rivers and coasts as well as reconstruction process after the Great East Japan Earthquake (GEJE). It reveals how ecosystem approaches are integrated in river and coast works and highlights some of the relevant policies, technical guidance and guidelines and good practices on the ground. This study also documents how Eco-DRR policy evolved and implemented after the GEJE and addresses some of the challenges in its implementation. In order to draw additional insights, the reconstruction processes of Hurricane Sandy in the United States (US) was also reviewed as GEJE and Sandy shares some common features. Experience from Sandy suggests the importance of the participatory planning process rather than technical guidance or guidelines. Although it is too early to judge whether either reconstruction process was better or not, nor difficult to generalize the conclusion from only two samples, these two experiences suggest only technical guidance and guidelines is not sufficient to mainstream Eco-DRR/CCA in the reconstruction from large scale, rare and infrequent disasters. It is also suggested that the critical role of participatory planning process with cross-sector, cross-professional and interactive design approach may lead more innovative solutions.

The establishment of a conservation strategy or restoration goal for river estuaries requires knowledge of potential biota or possible habitat characteristics. In this study, we investigated the relationship between estuarine fauna and macro scale physical indicators on Kyushu Island, Japan to provide basic information for estuarine conservation. As a result of the classification of shellfish fauna by similarity, the Kyushu region was divided into three groups, namely, 1) southern Kyushu with high wave exposure, long fetch, and low tidal variation; 2) the Ariake and Yatsushiro seas with low wave exposure, short fetch, and high tidal variation; and 3) northern Kyushu with an intermediate fetch and tidal variation. In addition, a number of sites, such as Nakatsu Port, Sone tideland, and the Honmyou River, were classified into geographically different groups. This is because the physical characteristics of these sites were similar to classified groups or shellfish fauna were significantly altered by artificial impacts. As a result of discriminant analysis, the discrimination hit rate of species inhabiting the inner bay or tidal flat was high, whereas that for species using a wide variety of bottom sediment environment was low. To improve the accuracy of the discriminant model, it is necessary to collect more detailed physical information, such as habitat type, salinity concentration, or grain diameter of bottom sediment. To establish a conservation or restoration strategy, there is a need for classifying taxonomic groups or physical characteristics.

The purpose of this study is to demonstrate the process of deposition and influence of human and natural impacts to sediment in Imazu tidal flat. In this study, various impacts on Imazu tidal flat were examined with the use of topographic, aerial photographs, rainfall record. Then, analysis of core sample's gradation, ignition loss, 137Cs and 210Pb was studied to clarify the age of sedimentation and historical change of environment of sediment. The results were as follows. The urban development around Imazu tidal flat has had worse influences on the sedimentary environment. The sedimentation rate of Imazu tidal flat was calculated 0.47-1.12cm/y since 1963, and in 1954-1963 was 1.56-3.56cm/y by the analysis of core samples. It was calculated that 5640-13440m3 sediment was discharged from catchment area annually, and 47520-333720m3 sediment flowed in Imazu tidal flat in 1953 by these results. It was assumed that this was caused by the flood in 1953.

多摩川永田地区では2001年から2002年にかけて河原の再生に注目した河道修復が国土交通省関東地方整備局京浜工事事務所で行なわれた.本文では,修復にいたる経緯,修復目標の設定,修復の方法について述べ,考察を行なった.1995年に河川生態学術研究会多摩川グループが発足し,永田地区を対象とする研究が開始された。近年,永田地区では砂利掘削などにより河道形状が変化し,河原が減少し,カワラノギクに代表される河原に依存する生物が絶滅の危機に瀕していること,かわって外来種であるハリエンジュが増加していることなどが明らかとされた.1998年,多摩川グループが行なっている市民向けの発表会で,ハリエンジュの伐採は可能かということが討論された.それを契機に,京浜工事事務所は,植生管理基本検討会を設け,討論の結果ハリエンジュを伐採し,河道修復を行なうこととなった.河道修復は2段階で行なわれることになり,第1ステップとして絶滅の危機に瀕しているカワラノギクを代表とする河原の生物の保全を目標とし,次の段階で,扇状地河川特有の微地形に起因する環境を目標とすることとなった.具体的な修復方法は,51.7km～52.4kmの右岸側の,高水敷上のハリエンジュを伐採し,表土を剥ぎ取り,掘削を行い,低水路を拡幅し礫河原を造成し,永田地区の直上流の河床に砂利を敷き詰め土砂供給を行なう。透かし礫層の造成方法,造成された面の水面からの比高は,数通りのものが実験的に与えられた。永田地区の河道修復は水系全体のシステムの修復ではなく,永田地区を対象とした,部分的な動的システムの修復であり,社会の変化を考えたとき,多摩川では部分修復が現実的であることを考察した.また,永田地区では,人間が与えたインパクトを取り除いただけでは,自立的な修復は望めず,人間が何らかの形で関与しながら河原を維持することが現実的であることを考察した.

River estuaries are important aquatic environments characterized by large environmental gradients in their water quality, riverbed material, and microtopography in the longitudinal and transverse directions. The geography or habitats in river estuaries differ depending on the energy from the tide, waves, and river; therefore, the biota inhabiting river estuaries vary depending on the river estuary type. In view of this, for effective conservation in river estuaries, there is a need for information about potential habitats and biota based on objective data about the river estuary type. The objective of this study thus was to classify river estuaries by their molluscan fauna and physical indicators to reveal the relationship between molluscan fauna and the physical environment. The classification results using physical indicators indicated three types of river estuaries (wave energy-dominated group, tide energy-dominated group, and low tide and wave energy group). This classification result was similar to the classification of molluscan fauna. Therefore, it was suggested that molluscan fauna is extremely useful as a variable representing the river estuary environment. From the comparison between molluscan fauna and the physical environment, some rivers were not classified into the same group in the classification of molluscan fauna, despite them having similar physical environments. Some of these rivers with a molluscan fauna that diverged from expectations had undergone channel modification, which is expected to have caused a shift in this fauna group. These results suggest that this approach could be used to identify rivers that have been degraded by human activities.

治水・利水を目的とした河川構造物による河川の分断化がおき、その対策として魚道が設置されている。その中で階段式魚道が最も実績があり、研究も多く行われている。階段式魚道はプール規模・流量変化により、プール内流況が大きく変化し、大きく2つに分けて、表面流 (Plunging Flow)、落下流 (Streaming Flow) 状態を形成することが過去の研究で確認されている。一方、隔壁頂部形状の変化により、魚の遡上率に強い影響を受けることも確認されている。本研究ではウグイの遊泳行動と流況がこの隔壁頂部の形状 (丸型・斜型45°・斜型30°) とプール規模 (プール水深・プール延長) に関連していることを示した。

In Japan, lakeshore vegetation has been decreasing in many places. Lakeshore erosion due to wind waves is one of the main reasons. Recent study reveals critical wave condition for creation of the stable lakeshore. The artificial floating island (AFI) is a breakwater to control wave condition, which functions for production of vegetation habitat and improvement of water quality as well. AFI was experimentally installed at Shimanami Area in Lake Kasumigaura in 1998 in order to protect lakeshore and vegetation against waves. In this area lakeshore vegetation has been rapidly decreasing due to wave action. AFI is designed to attenuate significant wave height from 64 cm to 30 cm. As a result, lakeshore vegetation area has expanded 3.4% after 1-year period experiment. Annual wave energy behind AFI becomes half of that in the offshore. However, wave intrusion from lateral sides is significant in AFI and it causes lateral erosion of lakeshore. Installation of a breakwater made of riprap is recommended at lateral side in order to decrease wave reflection by covering the vertical seawall.

平常時の河川流量を景観から設定するための研究である. 3つの階層からなる景観評価プロセスモデルを構築し, 9都市の215人の被験者に対する42河川スライドを用いた景観心理実験を行った.結果は, (1) 流れの量的イメージは「流量感」であらわしうる, (2)「水量感」は心理量「水面が広い」と「水深が深い」で説明できる, (3) 心理量「水面が広い」は「みかけの水面幅」と「みかけの川幅」の比W/Bと高い相関を示す, この結果を用い(4) 正常流量設定の手順を提案した.