Tanjung Emas harbour is one of strategic harbours in Indonesia, which is located in Semarang City. Several problems arise nowadays; the drainage channel capacity decreases due to lack of treatment, rainwater storage reduced, land subsidence and the rise of tide sea level. The flood control used is polder system that classified into several clusters. The research location is focused on the Cluster IV, which the right side of harbour area. According to the data, catchment area is 29.3 hectares, the lowest elevation area is in +0,5 m, the dike elevation is +2 m LWS. Then retention pond area prepared is 900 m2 (0.3% of CA), retention pond depth - 2m LWS. Based on simulation using 2×0.3 m3/sec pump and rainfall intensity return period of 25 years 303 mm, fluctuation in water retention pond can be maintained in +0,5 m water level. It is recommended to add 0.3 m3/sec alternative pump. A pump of 3×0.3 m3/sec needs to be prepared. Based on the simulation, by Polder system, the flood problem in harbour area can be solved.

Pekalongan River has two functions, i.e., as fishing boat transportation and the main drainage of Pekalongan City. The Pekalongan river estuary has a Jetty located on two sides of the river mouth. The jetty is used to protect from waves and sediment. The Pekalongan river has upstream flow from Kupang and Banger river. Because of the flood incident around 2003, Since 2014, the two rivers became two estuaries. The condition caused a negative impact on sediment in the river mouth. Therefore, this research aims to find solutions by simulating waves, currents, and sediments. In this paper, the focus is on the wave simulation. This research method begins with the collection of primary data in the form of bathymetry measurements at the river mouth. While the secondary data is wind data for 13 years and tidal. Calculation of wind hindcasting figures out a wave at a significantly high value of 1.38 m and a significant period of 4.80 seconds. For wave simulations, it used SMS software in the CGWAVE module. The simulation compares the two jetties condition, in existing and development conditions. Based on the simulation, the wave is still high for existing conditions and becoming low by an extended jetty of 200 m lengths. The simulation results can be used to analyze the movement of sediment transport that is affected by the movement of waves around the river mouth.

To protect the estuary from sedimentation and waves need a jetty structure. This study discusses the alternative jetty design to be simulated for waves and sediments. The research was located in Batang Regency, Central Java Province. The study objective is to simulate wave and sediment for alternative estuary protection. Preliminary data are collected include topography and bathymetry, tidal observation data that include research area. The secondary data were wind data from BMKG of Semarang Station. The wind data used was each hour data for 16 years in the years 2004 to 2019. To simulate the wave and sediment, a software MIKE was used for the two alternative design. The first alternative using 2 jetties with 100 m length and the second alternative using two jetties with addition length for east side. Based on the sediment transport simulation result, the second alternative design put less 5 cm a year then the first alternative. The evaluation based on cost, time period construction, construction methods, According to the scoring, the first alternative design will be choose to the design and construction step.