Time of concentration, Tc, is defined as time elapsed from the beginning of rainfall infiltrated into soil layer until it reaches a constant infiltration rate (fc) which is indicated an equilibrium subsurface flow rate. In hydrological view, time of concentration plays a significant role in elaboration of transformation of rainfall into runoff in a watershed. The aims of this research are to define influence of soil density and soil water content in determining time of concentration using infiltration concept based on water balance theory, and to find out the effect of land slope this time. Watershed laboratory experiment using rainfall simulator was employed to examine time of concentration associated with infiltration process under different slope, soil density and soil water content based on water balance concept. The steady rainfall intensity was simulated using sprinklers which produced 2 dm3∙min–1. Rainfall, runoff and infiltration analysis were carried out at laboratory experiment on soil media with varied of soil density (d) and soil water content (w), where variation of land slopes (s) were designed in three land slopes 2, 3 and 4%. The results show that relationship between soil density and land slope to time of concentra-tion showed a quadratic positive relationship where the higher the soil density address to the longer time of concentration. Moreover, time of concentration had an inverse relationship with soil water content and land slope that means time of con-centration decreased when the soil water content increased.

A sediment trap with bamboo materials can be utilized as one alternative of eco-friendly technology to reduce the ero-sion that occurred on agricultural land. This study aims to determine the most efficient form of that sediment trap in the field. Location study is in the Tulungrejo Village, Batu, Indonesia, which has andosol soil type and 35 cases of a landslide in 2013. Three forms of sediment traps were used (square, trapezoidal, and stratified type) with the purpose to find the most effective form. It is obtained that the most effective sediment trap is a stratified form with the 31.91% effectiveness or able to withstand sediment of 25.02 kg, while the adequate number is two pieces with the ability to withstand the most consider-able sediment of (91.70%). Therefore this stratified form of sediment traps is effective in erosion prevention on agriculturalland in the study area. For further development, it is required to test out the variations of the contents in a broader area with a more varied level of the slope.