Satoquo Seino

Establishment of numerical beach-litter hindcast/forecast models: An application to Goto Islands, Japan

This study attempts to establish a system for hindcasting/forecasting the quantity of litter reaching a beach using an ocean circulation model, a two-way particle tracking model (PTM) to find litter sources, and an inverse method to compute litter outflows at each source. Twelve actual beach survey results, and satellite and forecasted wind data were also used. The quantity of beach litter was hindcasted/forecasted using a forward in-time PTM with the surface currents computed in the ocean circulation model driven by satellite-derived/forecasted wind data. Outflows obtained using the inverse method was given for each source in the model. The time series of the hindcasted/forecasted quantity of beach litter were found consistent with the quantity of beach litter determined from sequential webcam images of the actual beach. The accuracy of the model, however, is reduced drastically by intense winds such as typhoons which disturb drifting litter motion.

Using Radio-Acoustic Positioning and Telemetry (RAPT) to Define and Assess Marine Protected Areas (MPAs)

Radio-acoustic positioning telemetry (RAPT) continuously triangulates positions of up to eight acoustic transmitters by relaying sound arrival times to a shore-based computer via autonomous, moored radio-sonobuoys. As transmitters on animals or people telemeter information via RAPT, it records their position with an accuracy of as little as one meter in as much as a cubic kilometer of water from a range of up to ten kilometres—scales appropriate to many marine protected areas (MPAs). RAPT studies in Lizard Island, Australia; Exuma Cay Park, Bahamas; Moriye Bay, Japan, and Leigh Laboratory Reserve, New Zealand, four significant MPAs, are reviewed showing the power of the technology for understanding and managing many aspects of a range of biological reserve types. Most studies to date have focused on monitoring fish (Lutjanus carponotatus, Lutjanidae; Plectropomus leopardus, Serranidae; Epinephelus striatus, Serranidae; Pagrus auratus, Sparidae) home ranges and migrations, but breeding and feeding behaviours of larger invertebrates such as horseshoe crabs (Tachypleus tridentatus, Limulidae) and squids (Sepioteuthis lessonianna and Loligo vulgaris, Loliginidae) have also been examined. RAPT systems can also record environmental changes in real-time directly to the computer on shore for such variables as temperature, salinity, tide height, current direction and current speed from fixed-position transmitters; these are easily compared to animal activities. Tracking tagged divers or ROVs while they are videotaping provides an accurate and reproducible way of documenting long-term changes in the sessile organisms that make up benthic habitats; only the buoy moorings need remain in the water between surveys. Finally, the location and condition of diving tourists can be monitored, to protect both them and the environment!

Progress and Gaps in Eco-DRR Policy and Implementation After the Great East Japan Earthquake

In 2011, Japan experienced a huge earthquake followed by a tsunami and a nuclear power accident known as the Great East Japan Earthquake (GEJE). This chapter focuses on impacts of the tsunami and the reconstruction of coastal zones affected by GEJE, with a greater emphasis on sea wall reconstruction. The main question addressed in this chapter is how ecosystems played and are playing a role in GEJE and the reconstruction process from both policy and implementation perspectives. In this respect, it reviews how sea walls, coastal forests, traditional knowledge and protected areas played out during the GEJE. The chapter also provides a review of policy responses after GEJE to promote ecosystem-based disaster risk reduction (Eco-DRR) both at the global as well as national level by the government of Japan. It then reviews reconstruction activities on the ground with a particular focus on coastal areas such as reconstruction of sea walls and coastal forest. Finally, policy-implementation gaps and lessons are discussed from an Eco-DRR point of view based on these practical experiences.

SAND CIRCULATION OFFSHORE OF MOUTH OF A RIVER FLOWING INTO TIDAL MUD FLATS

Abstract: The sand discharge of a river mouth bar due to flood currents and the return of sand transported in the offshore zone were modeled using a pair of sink and source of sand incorporated into the contour-line-change model, taking the Maite River flowing into the Nakatsu tidal flats as an example. The effect of the change in the intensity of cross-shore sand transport relative to longshore sand transport Kz/Kx on the sand movement was investigated. It is concluded that when sand is transported offshore by flood currents on the tidal flats, such sand returns to the shoreline under the action of waves, and finally, sand circulation develops.

The “MIZBERING” Zuibaiji Conference ~ A Search for Continuity in the Zuibaiji River Basin~

The Zuibaiji River is located in the west of Fukuoka city, which has a rich natural resources and history but various problems as well. In order to solve some of these problems, stakeholders need to observe and talk about the river. Also recently, the “MIZBERING Project” has been opening up possibilities for renewing riverside uses of lost activities from the old days in Japan. This project is being conducted by citizens, companies and government administrations with an interest in waterside areas. The First MIZBERING Zuibaiji River Conference was held to discuss the issues of the Zuibaiji Basin. Its purpose was to visit and search out the nature and history of the entire Zuibaiji Basin from its mountains to the sea and to rediscover the Zuibaiji Basin, and finally to discuss future plans for the Zuibaiji Basin and Imazu Tidal Flat at its outlet. After visiting the Zuibaiji Basin, we discovered a problem that the Zubaiji Dam is holding not only water but also sand, and this problem affects the environment of the Zuibaiji Basin, such as its ecosystem and topography. Finally, we provided a venue for the local people to discuss problems and future plans for the Zuibaiji Basin.

FIELD EXPERIMENT OF CONTROLLING LONGSHORE SAND TRANSPORT USING STONE GROIN IN SANBYAKKEN REGION IN NAKATSU TIDAL FLAT

A field experiment on sand back passing was carried out in Sanbyakken Region in Nakatsu tidal flat in Oita Prefecture. 3600 m of sand was dredged at the tip of the sand spit, which causes the closure of the Kakise River mouth, and such sand was transported to the west end of the sand spit. To prevent sand from rapidly returning to the tip of the sand spit, a 24-m-stone groin was experimentally installed at the middle of the sand spit. The effect of controlling longshore sand transport was investigated. Aerial photographs were taken four times during the monitoring period. The stone groin had a mild effect on the shoreline changes compared with that of the ordinary groin because of short length and low crown height.

Shoreward Sand Transport after Offshore Sand Capping on Nakatsu Tidal Flat

2009年10月3日14:30の干潮時(潮位DL0.6m)撮影の 空中写真を図-1に示す.三百間地区はほぼ三角形状の堤 防に囲まれており,その頂点Pから東西両方向に砂州が 伸びる.東向きに約670m伸び,その先端部で蛎瀬川河口 を囲むように伸びた砂嘴を有するのが三百間砂州である. この砂州の汀線に沿っては東向きの沿岸漂砂が卓越して いる.三百間砂州は,過去に中津川の洪水によって干潟 上へと運ばれた砂が波の作用下で岸向きに運ばれて長大 な砂州として伸び,それ自体が変形しつつ現在の位置に 達したものである(清野ら,2007).しかし現在では中津 川の流下土砂はわずかであり,砂州は孤立した砂の塊と して長らく存在していた.一方,頂点Pの西側にも狭い 砂浜があるが,この砂浜と三百間砂州とは堤防頂点を境 に不連続になっている.図-1の頂点P付近が砂の上陸が 起きた場所である.この場所は三百間砂州の西端を区切 中津干潟沖での覆砂の岸向き移動機構 Shoreward Sand Transport after Offshore Sand Capping on Nakatsu Tidal Flat

Mechanism of Deformation of Sand Bar Formed in Sanbyakken Region in Nakatsu Tidal Flat

Long-term changes in sand bar in Sanbyakken region in Nakatsu tidal flat were investigated through the comparison of the aerial photographs. Great changes have occurred in this sand bar in recent years, as aresult of increase in eastward longshore sand transport since 1998. The reason was studied in terms of change in wave field. Waves with the direction of N70deg E, which was determined from the shape of the sand bars on the tidal flat, were significantly sheltered due to the offshore breakwater of Nakatsu Port. Takingthe refraction effect of these diffracted waves into account, the tip of the sand bar was also sheltered by the waves. It was found that this caused increase in longshore sand transport.

TRANSITION IN INHABITANTS' ENVIRONMENTAL PERCEPTION OF SAND BARS AND TIDAL FLATS IN TERMS OF THE LOCAL HISTORY OF SALTPANS IN AWASE, OKINAWA, JAPAN

沖縄本島の泡瀬干潟には, 人工島建設の開発計画があり, 地域振興と生態系保全の両立が焦眉となっている. 地域史のシンボル「塩田」に着目し, 郷土史, ヒアリング, 写真記録をもとに地域住民の自然観と地域開発の要望の根源を解析した. 住民は, 入浜式塩田での製塩経験から, 塩の品質管理のため水質や塩田基盤の底質環境に対する関心が歴史的に高かった. 地域開発では, その地の自然特性と住民の自然認識の関係性や歴史性により注目すべきである.

BEACH EROSION OF HITOTSUBA COAST IN MIYAZAKI PREFECTURE AND PROTECTION OF LOGGERHEAD TURTLE, Caretta caretta

宮崎県一ツ葉海岸を対象として海岸侵食の原因を考察し, アカウミガメCaretta carettaの産卵地保護のあり方を示した. 近年, この海岸では侵食が深刻であり, 海岸線に沿って高い浜崖が形成され, アカウミガメの産卵が非常に危惧される状況となっている. 侵食原因は, 宮崎港の防波堤による波の遮蔽域形成と航路浚漢により波の静穏域へと砂が移動して周辺域の土砂が吸い込まれたこと, また一ツ瀬川河口導流堤による南向きの沿岸漂砂の阻止と河口での航路浚渫である. 近い将来における日本最大のアカウミガメの産卵地の消滅を防ぐには, 問題への根本的な対応が必要である.