Spatial approaches, based on the deformation measurement of volcanic domes and crater rims, is key in evaluating the activity of a volcano, such as Merapi Volcano, where associated disaster risk regularly takes lives. Within this framework, this study aims to detect localized topographic change in the summit area that has occurred concomitantly with the dome growth and explosion reported. The methodology was focused on two sets of data, one LiDAR-based dataset from 2012 and one UAV dataset from 2014. The results show that during the period 2012–2014, the crater walls were 100–120 m above the crater floor at its maximum (from the north to the east–southeast sector), while the west and north sectors present a topographic range of 40–80 m. During the period 2012–2014, the evolution of the crater rim around the dome was generally stable (no large collapse). The opening of a new vent on the surface of the dome has displaced an equivalent volume of 2.04 × 104 m3, corresponding to a maximum −9 m (+/−0.9 m) vertically. The exploded material has partly fallen within the crater, increasing the accumulated loose material while leaving “hollows” where the vents are located, although the potential presence of debris inside these vents made it difficult to determine the exact size of these openings. Despite a measure of the error from the two DEMs, adding a previously published dataset shows further discrepancies, suggesting that there is also a technical need to develop point-cloud technologies for active volcanic craters.
To enable conservation of degraded land requires Map of Conservation Activity Plan (CAP). The map is established based on a model developed by the then Ministry of Environment and Forestry. One step to analyze the CAP is land unit elimination (LUE) having area of < 1 cm2. This study aimed to determine the effect of LUE on the CAP at Air Bengkulu Watershed. Maps used for input to CAP are EHL (Erosion Hazard Level), Soil Depth, Slope, Population Pressure, and the Recommended Landuse, whereas to calculate EHL requires R, K, LS, C, and P Factors. CAP Map as a result without involving LUE is compared to the CAP Map with involving LUE. The research result showed that the LUE influences on the change of the recommended of the CAP up to 77.6% of the total area of the study, either in engineering recommended or in vegetatively recommended conservation, while the rest (22.4%) were unchanged.
ABSTRAKDaerah Aliran Sungai (DAS) Opak terdiri atas beberapa sub-DAS, salah satunya adalah Code. DAS yang luas menjadikan kompleksnya masalah sehingga diperlukan penyederhanaan, misalnya pada sempadan sungai. Penelitian ini bertujuan untuk: (1) mengetahui luas berbagai penutup lahan di sempadan Sungai Code, (2) mengkaji peran vegetasi terhadap ekosistem sempadan Sungai Code, dan (3) menentukan arahan pengelolaan terkait garis sempadan Sungai Code. Metode yang digunakan dalam penelitian adalah metode interpretasi citra Quickbird yang didukung survei lapangan untuk validasi data penutup lahan. Lokasi penelitian dipilih sempadan Sungai Code wilayah sempadan Sungai Code Yogyakarta dan sekitarnya, tepatnya yang terdapat di dalam jaringan jalan lingkar utara dan jalan lingkar selatan. Data penutup lahan wilayah sempadan Sungai Code disajikan pada buffer area sungai dengan lebar 3 meter, 5 meter, 10 meter, dan 20 meter di kiri dan kanan sungai. Hasil menunjukkan bahwa sempadan Sungai Code memiliki penutup lahan dengan luasan dari yang tersempit ke terluas adalah badan air, jalan, lahan terbuka, lahan terbangun, dan vegetasi. Vegetasi dapat berperan bagi ekosistem sempadan sungai melalui delapan fungsi, yaitu infiltrasi, perlindungan tebing sungai, ruang gerak lateral sungai, perlindungan banjir, restorasi, pertahanan kualitas habitat amfibi dan organisme akuatik, penyedia nutrisi, serta (8) sebagai elemen estetika koridor sungai dan elemen ameliorasi iklim mikro. Luas vegetasi sempadan Sungai Code mencapai lebih dari 50 persen wilayah sempadan pada buffer 3 meter, 5 meter, 10 meter, dan 20 meter. Hal ini bukan berarti bahwa sempadan Sungai Code aman dari bahaya. Diperlukan adaptasi dan mitigasi terhadap bencana hasil arahan pengelolaan sempadan Sungai Code. Pengelolaan sempadan sungai disarankan berbasis masyarakat melibatkan masyarakat dalam penentuan garis sempadan sungai sehingga jika masyarakat malampaui garis sempadan, adaptasi dan mitigasi terhadap bencana dapat membantu mengurangi risiko.Kata kunci : sempadan sungai; ekosistem; pengelolaan berbasis masyarakat
Lake Rawapening, Semarang Regency, Indonesia, has incorporated a holistic plan in its management practices. However, despite successful target achievements, some limitations remain, and a review of its management plan is needed. This paper identifies and analyzes existing lake management strategies as a standard specifically in Lake Rawapening by exploring various literature, both legal frameworks and scholarly articles indexed in the Scopus database and Google Scholar about lake management in many countries. By using Publish or Perish with the keywords “lake management” OR “management of lake”, 1532 and 1990 works from the Scopus database and Google Scholar, respectively, have been reduced 37. The results show that there are two major types of lake management, namely pillar-based and object-based. The holistic review has resulted in nine points of pillar-based management, which consists of conceptual paradigms as the foundation, and 11 points of object-based management to restore or preserve the lake, which is in line with the form of programs and activities. Overall, Lake Rawapening management should be concerned with finance and technology when applying pillar-based management, and it should include more activities within programs on erosion-sedimentation control as well as monitoring of operational performance using information systems to ensure the implementation of activities within programs in applying object-based lake management.
Hillslope and mountain roads are often the source of erosion, which in turn can lead to larger landslides and other types of mass-movements. For this reason, low-cost repeat surveys that can be done by practitioners and not solely scientists and engineers is essential. To solve this issue the present contribution shows the testing and applicability of a mix of SfM-MVS and low-cost SLAM technology to provide erosion information. The low-cost SLAM generated between 300 ~ 900 points per square meter, while SfM-MVS created between ~11,000 to 900,000 points. The density is however a trade-off against a spatially varying error, although the variability at the road-cut scale only ranges from 2 cm vertically to 2.5 cm in x,y,z based on the C2C algorithm. Furthermore, this error tends to be more important in the higher section of the cutout (further away from the sensor and at a flatter angle). It is thus possible to measure small-scale roadside change, providing that the change is in the range of >5 cm (adding the maximum potential error twice) and providing that the road-cut is such that the sensors can be brought close to the surface (camera or sensor on a pole). The authors suggest that it can be a solution for state and agencies with limited funding and that cannot afford regular laser or for roadside that are difficult to access.
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