Simulation of Rainfall Intensity and Slope Gradient to Determination the Soil Runoff Coefficient at Microplot Scale

Simulating rainfall is one of the valuable methods of measuring hydrological data and soil erosion processes. Rapid evaluation, high repeatability, and low cost are the reasons of using rain simulators. In this study, a rain simulator was constructed in dimensions of 3.0 × 3.0 × 3.0 m and it was protected on three sides by a plastic cover. An inclined table was used to create slopping surfaces of 5, 10, and 15%. Microplots were used in the dimensions of 0.2 × 0.4 × 1.0 m to collect and measure direct runoff in a bucket outside the device. Nozzles were calibrated to produce two different rainfall intensities 10 and 20 mmh−1 using sprinkler Model 5B at 8 and 12 psi, respectively. Furthermore, three different soil types, namely, clay loam (CL), silty clay (SC) loam, and SC were examined. In general, it was observed that with increasing the rainfall intensity and slope, the rate of runoff and sedimentation increase. SC soil at 15% slop offered the highest performance under the intensity of 20 mmh−1. SC and the CL soils produced the highest and lowest runoff coefficients, respectively. The CL soil produced the highest soil loss (1 kgm2 at 15% and I = 20 mmh−1). Further, it was concluded that a significant change (an average increase of 53%) in soil loss can be achieved as the rainfall intensity increased from 10 to 20 mmh−1.

Comparison of Live Coral Cover in Central and South Bangka

Coral reef ecosystem has many biological, ecological, and economical functions to the universe. This ecosystem provides shelter, food, and home for many marine organisms and together they perform diverse and rich ecosystem. However, this diverse ecosystem is very susceptible to environmental change, such as climate change, ocean acidification, and other anthropogenic impact. When reef-building coral could not stand with harsh condition they will eventually die. We assume that anthropogenic stressor such as turbidity, terrestrial runoff, and sedimentation is the main problem here, because of high number of tin mining activities. Bangka and Belitung Islands are huge tin producer and has been exploited heavily by the legal and illegal miner company. The purpose of this study is to investigate the live coral cover in Central and South Bangka by using the line intercept transect to calculate the live coral, died coral, and algae in each stations. The results showed that the coral cover in Central Bangka and South Bangka has fair condition (25-40% of live stony coral). Value of live and dead coral cover was 40% with Semujur and Ketawai represent the coral cover in Central Bangka. While South Bangka has slight (1-2%) difference of live coral, dead coral, and algae cover. High number of dead coral mainly composed by dead coral overgrown by algae, allegedly caused by high turbidity and sedimentation from the anthropogenic stressor. Keywords: coral reef, coral cover, died coral, sedimentation Abstrak Perbandingan Tutupan Karang Hidup di Bangka Tengah dan SelatanEkosistem terumbu karang mempunyai fungsi biologi, ekologi, dan ekonomi yang bermanfaat bagi manusia. Ekosistem ini menyediakan tempat berlindung, makanan, dan rumah bagi organisme laut dan membentuk suatu ekosistem yang kaya dan beragam. Namun, ekosistem ini sangat rentan terhadap perubahan lingkungan, sepertiiklim, asidifikasi, dan dampak lain yang dilakukan manusia. Ketika terumbu karang tidak mampu bertahan dengan perubahan lingkungan yang ekstrim mereka akan mati. Kami menduga bahwa dampak antropogenik seperti turbiditas, runoff dari darat, dan sedimentasi merupakan penyebab utama kerusakan terumbu karang, karena banyaknya aktivitas penambangan. Kepulauan Bangka belitung adalah penghasil timah terbesar dan telah dieksploitasi oleh penambang timah legal maupun ilegal. Tujuan dari penelitian ini adalah untuk mengetahui tutupan karang hidup di Provinsi Bangka Tengah dan Bangka Selatan dengan menggunakan metode traksek garis. Hasil menunjukkan bahwa terumbu karang di Bangka Tengah dan Selatan termasuk kategori sedang (25- 40% tutupan karang). Tutupan karang hidup dan karang mati di Bnagka Tengah sebesar 40% dari hasill pengamatan di Semujur dan Ketawai. Sedangkan nilai tutupan karang hidup, karang mati, dan alga di Bangka Selatan mempunyai angka perbedaan yang rendah (1-2%). Tingginya tutupan karang mati tersusun oleh karang mati yyang ditumbuhi alga yang disebabkan oleh turbiditas dan sedimentasi.Kata Kunci: karang mati, terumbu karang, tutupan karang, sedimentasi

The effects of Rubus hyrcanus L. and Philonotis marchica (Hedw.) Brid. on soil loss prevention from cutslopes of a forest road

The effects of Rubus hyrcanus L. and Philonotis marchica (Hedw.) Bridon on runoff generation and soil loss from cutslopes of forest roads were investigated. The study was conducted at the northern forest of Iran, about 30 km south of the city of Sari. Runoff and sedimentation after each rainfall simulation and chemical and physical soil properties were measured in 14 plots with an area of 0.48 m². The obtained results indicate that the vegetation dominated by Philonotis marchica exhibited the higher runoff coefficient and soil loss, with averages of 27.25% and 92.40 g·m^–2·h^–1(gram per square meter per hour), respectively, in comparison to Rubus hyrcanus. For Philonotis marchica (Hedw.) Brid. the sediment concentration increased quickly at the beginning of rainfall simulations and after 10–12 min there was a fast decrease in sediment concentration. The peak of sediment concentration was for the Rubus hyrcanus L. in the 13^th–15^th min In conclusion, Rubus hyrcanus L. prevented or decreased the risk of runoff and soil loss from cutslopes of forest roads in our study area.