Sugeng Widada

Waves Induce Sediment Transport at Coastal Region of Timbulsloko Demak

Waves have variation of length and period. This influenced by seasonal variation. Impacts of seasonal variation related to wave is playing important roles in sediment transport mechanism and coastal changes. This condition not only treats coastal area but also decreases economic capacity of community. This research aim to determine different seasonal based on Indonesia Northwest-Northeast monsoon and Southeast-Southwest monsoon and theirs relation to sediment transport. Area of study is suffered by 938.73 H of abrasion. Conducted by CERC methods, transforming BMKG Ahmad Yani wind database (2005-2015) into wave’s data of seasonal variation and using field measurement recorded by ADCP. Definitely, maximum speed of wind is reached at 23 knots from December to February, wind direction predominantly from North West direction. Range of significant Wave Height (Hs) all season is 24.66-30.32 cm and Significant Wave period (Ts) count at 3.64-3.78 sec. Net of sediment volume annual 72,353.40 m3 year -1 and sediment movement pattern is forwarding from west to east direction. Correlation between breaking waves and sediment transport is linier.

Landslide potency at Trangkil, Gunung Pati based on the groundwater flow pattern and the value of safety factor

One of strategic approaches in landslide disaster mitigation atTrangkilsettlement area, Gunungpati, Semarang is through the prevention of soil and rock saturation. The investigation of soil and rock saturation is determined based on the shallow groundwater flow pattern and the value of safety factor.The location which prone to landslide on the eastern part with slower groundwater flow is reinforced by the rock characteristics analysis result which show its permeability value is 8.8 x 10-7 cm/s. The slow groundwater flow withinin the loam lithology makes the rock mass is greater, while its lithology could rests on an impermeable claystone. This condition makes the incompact silty loam and peeble mass could easily slide along the claystone surface and based on the analysis of rock characteristics result on the eastern part, the permeability value is smaller than on the western part. The value of safety is 1.372 indicates that the eastern part is an area prone to landslide.