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The eastern Kendeng Hills (Java, Indonesia) expose a 1000 m thick series that is used as a stratigraphic standard, representing the emergence of eastern Java from the sea. The fluvial top is rich in vertebrate fossils and yielded the Mojokerto (Perning) hominin skullcap, which is regarded as the earliest evidence of Homo erectus on Java, with age estimates ranging between 1.9 and 1.49 Ma. The series is commonly regarded as an uninterrupted record of coastal progradation. However, recent studies show that the emergence of eastern Java has been a complex process, under influence of tectonism, volcanism, sea-level fluctuations and fluvial dynamics, leaving a fragmented depositional record that varies from site to site. This is at odds with the prevailing stratigraphic practice of long-distance correlations and questions the existing interpretations of the eastern Kendeng reference sections. Here we present the results of a fieldwork-based re-interpretation of this key stratigraphic record, which we identified as the fill of a previously unrecognized Plio-Pleistocene embayment, surrounded by elongate uplift zones. Clinoform-bedded sandstones relate to a stage of explosive, high-silica volcanism, supplying large volumes of ash. The embayment fill is incised and covered by fluvial deposits, which we relate to the Middle Pleistocene Brantas. The fluvial strata have a cyclic build-up, probably representing sea-level controlled stages of aggradation and degradation. Based on a reconstruction of fluvial cycles, we provisionally link the conglomerate bed in which the Mojokerto Homo erectus was found to MIS14 (similar to 550ka). We infer that the published radiometric ages derive from reworked volcanic clasts that make up this incisive fluvial lag and are not representative for the age of deposition. Our study places the eastern Kendeng series in a new landscape context and changes our view of the timing of hominin migration to Java. (C) 2022 Published by Elsevier Ltd.

Konsep restorasi dibangun guna mengembalikan sungai seperti sediakala. Secara kasat mata, sungai-sungai penuh sampah, limbah, terutama di pemukiman dan perkotaan. Kalaupun sungai dikelola, tidak memperhatikan ekosistem. Masyarakat tidak lagi memperhatikan sungai, padahal sungai alam sangat berguna bagi manusia. Sungai, katanya, memiliki banyak peran strategis seperti suplai air, menanggulangi banjir, tanggulangi kekeringan, alat transportasi, iklim mikro, kesehatan ekosisitem, jalur hijau, pendidikan dan banyak lagi. Sayangnya, peran penting ini tak diimbangi kesadaran masyarakat memperlakukan sungai. Untuk itu, sungai restorasi hadir, katanya, sebagai gerakan mengubah pola pikir masyarakat. Ada 5 konsep restorasi sungai dalam meningkatkan eksistensi dan mengembalikan esensi sungai. Yakni: 1) Restorasi Hidrologi, dengan memantau kuantitas dan kualitas air. 2) Restorasi Ekologi, dengan memantau terhadap flaura dan fauna. 3) Restorasi Morfologi, dengan meninjau bentuk keaslian sungai 4) Restorasi Sosial Ekonomi, untuk melihat manfaat sungai secara ekonomis serta mengajak masyarakat ikut memperoleh pengetahuan 5) Restorasi Kelembagaan dan Peraturan, dengan fokus membuat peraturan-peraturan yang menjaga kelestarian sungai Pentingnya restorasi sungai disebabkan sekitar 70% sungai di Indonesia tercemar berat. Untuk itu, perlu perbaikan mulai DAS (Daerah Aliran Sungai), badan sungai dari hulu, tengah, hilir sampai muara, dan pantai, laut hingga pesisir. Sungai tak terpisahkan dengan gunung, hutan dan daratan lebih luas lagi. Ia tangkapan air hujan dan pemasok mata air, rembesan dan aliran. Degradasi dan ancaman sungai adalah ancaman ekologi dan ekosistem air, hingga perlu gerakan pemulihan dan pengembalian fungsi. Pengelolaan DAS dan sumberdaya air, katanya, seringkali penyebab utama kegagalan pengelolaan DAS. Ke depan, penting mengkaji dan evaluasi umum terhadap sistem ekologi sungai di Indonesia dalam perspektif keberlanjutan daya dukung. Juga mengkaji efektivitas aturan dan perundang-undangan yang menyangkut kelestarian ekologi sungai serta menginventarisir inisiatif-inisiatif masyarakat maupun akademisi.

The aims of this study are to provide data and information about diversity, dominance, and distribution of the Unionidae mussels species in Brantas River, East Java, Indonesia. Mussel samples were collected from 14 sampling stations along the Brantas River, starting from upstream in Tulungagung to downstream in Surabaya ( ± 170 km) in April-May 2012. The results showed that five species of mussels, namely: Contradens contradens, Elongaria orientalis, Rectidens sumatrensis, Pseudodon vondembuschianus and Pilsbryoconcha exilis were observed in the Brantas River. Contradens contradens was the €œdominant €? species, followed by Elongaria orientalis as a common species, and Rectidens sumatrensis, Pseudodon vondembuschianus and Pilsbryoconcha exilis as rare species. Distribution of each species in the Brantas River tends to be concentrated in downstream of the river, mainly located in station 13. According to the IUCN Red List, Rectidens sumatrensis was categorized in €œData Deficient €?, while Pseudodon vondembuschianus and Pilsbryoconcha exilis were categorized in €œLeast Concern €?.

流域規模での洪水、土砂動態の把握を目的として分布型洪水・土砂流出モデルを構築する。分布型モデルは空間分布情報を取り扱うため、GISやリモートセンシングの応用が有効である。本研究ではDEMの作成とその他の地理情報の取り扱いにGISを、土地被覆分類にリモートセンシングを用いる。構築される流出モデルはセル分布型の土砂流出モデルであり、火山灰堆積地において表面流が発生したときに土砂が生産される。従来のモデルでは雨水浸透厚の厚さで土砂が生産されると仮定していたが、本研究では表面流のもつunit stream powerに着目し輸送可能土砂量を計算した。これにより、土砂生産過程だけではなく土砂堆積過程をも考慮できるモデルヘと改良することができた。構築されたモデルをインドネシア、ブランタス川上流部のレスティ川流域に適用し、1995年11月から1996年4月の一雨季の降雨を入力することにより土砂流出計算を行い、モデルの性能についての検討を加えた。, A distributed rainfall-sediment-runoff model is constructed to investigate flood and sediment movement on a catchment scale. The model treats spatial data sets suchas topography and land cover effectively by applying GIS (geoglaphical information system) and remote sensing techniques. This research uses GIS to produce a DEM (digital elevation model) and remotely sensed data to classify land cover. The model constructed here is a grid-cell-based distributed model. The grid-cell-based kinematic wave model calculates rainfall-runoff and sediment is yielded when overland flow occurs on each grid-cell with surface volcanic soil layer. A primitive model (Takara, 2000) assumed that sediment was yielded with infiltration depth D regardless of energy of overland flow, which has limitation to transport sediment on each grid-cell.Considering a transportation capacity of overland flow on each grid-cell makes it possible to model both sediment yield processes and sediment deposit processes. The unit stream power theory decides the transportation capacity. Yielded sediment in slope grid-cells moves in the flow direction derived from the DEM to river grid-cells, on which bed load and suspended load are calculated. The model is applied to the Lesti River basin (625 km2) located in the upper Brantas River basin, and simulates sediment runoff during a rainy season from November 1995 to April 1996.

インドネシア東部のブランタス川中流域の土砂および洪水災害対策を考えるに当って, まず河床変動特性を明らかにすることが重要である。ブランタス川の河床変動にはクルー山の噴火に伴う土砂流出と上流に築造されたダム堆砂が大きな影響を与えている。ここでは, 過去の河床形状の調査結果に基づき1990年の噴火前後の河道の土砂収支を調べ, 河床変動に及ぼす噴火やダムの影響を調べるとともに, 一次元数値計算によって河床変動のシミュレーションを行った。, The topographical changes of Brantas River are principally dependent upon four factors. First factor is the huge volcanic eruption of Mt.Kelud. The tremendous production of sediment results in the sever bed aggradation. Second factor is the development of sediment erosion control works in the tributaries. In fact, a lot of sabo facilities have mitigated the sediment inflow to Brantas River. Third factor is the construction of damas and weirs. Several multipurpose dams and weirs have already completed. They must cause the bed degradation downstream of them. The last factor is the sediment excavation. In this paper we have investigated the effects of these factors on the bed variation of Brantas middle reach from Mojokerto to Kediri and simulated the bed variation using an one-dimensional model.