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The construction of Levee or river embankment is one method adopted for flood control in Palembang. The stability of the embankment is affected by water seepage inside the embankment due to several factors including rainfall as well as the repeated rise and fall of water surface in the sea due to gravity of moon and sun. Palembang is located 106 km from the east coast of Sumatra, thus the free water surface in Musi river and its tributaries is affected by the sea level. The stability of the levee is affected by the repeated change in the water level which induces changing seepage direction. This paper discusses the stability of levees constructed along Sungai Lacak, one of Musi river tributaries. In this case the stability of the existing levees was evaluated for different conditions of free water level i.e. normal, low tide and high tide. Analysis was also conducted for the case when the levee was constructed following the guidance in Standard Nasional Indonesia (SNI 1724-2015) and Guidelines of Public Work Department (2017). Improvement on the stability was obtained if the embankment was to be rebuilt according to the specification given in the standard. The presence of riprap protects the embankment from the effect of changing seepage direction due to the rise and fall of water level, thus increased the safety factor of the ideal levee during high tide from 1.270 to 2.325.

Scouring issues which occured at downstream of a weir can potentially endangers the weirs structureif the hydraulic jump is not properly dissipated, especially when the downstream river bed is unprotected. Due to strong correlation between discharge and the depth of the scour emerge, downstream protection is needed to maintain structure stability. To solve this problem, heavy protection is set at downstream of the weir such as riprap to prevent the scouring. This study aims to review the effectiveness of 3 alternatives measures through 3 dimensional physical model test by assessing the correlation among hydraulic parameters and the depth of the scour. The experiment were performed at hydraulic laboratory with a case study of Rengrang Weir in West Java. Based on laboratory test, hydraulic measures are effective to reduce the impact of the scouring. Alternative measures with riprap is more preferably because the easiness, economic and availability of thematerialon site.

Abstract: Method to prevent scouring, which is popular, is riprap, sack gabion, and gabion mattresses. The aims of this research are to analyze: (1) effectively installation patterns, (2) effectively dimensions, and (3) significance level. Method for analysis use descriptive analysis non dimensional. Results of research: (1) effective pattern installation is installing the structures at the face of pier and above river bed, (2) Dimension of the structures indicate that ever greater of the structures more effective to prevent scouring with optimum dimension is p/t = 4 (p = length and t = high), and (3) the structures give good performance to prevent scouring.