Sedimentation Modeling For Development of Kenjeran-Surabaya

Surabaya City administratively has a maritime boundary consisting of 11 districts known as Pantai Timur Surabaya (Pamurbaya). One of them is Kenjeran area. The area located in the Development Unit 3 in the Urban Spatial Plan (RTRW) used as a Service and Trade Area and also used as a Tourism Area. Therefore, this study is important to know the shoreline changes and made recommendations in zone management development. Results of this study found that the area of Kenjeran dominated by sedimentation with sedimentation range 0.002-0.015 meters. The largest sedimentation is 2.36x106 m2 with sedimentation of 0.02 meters. Development of the area in Kenjeran is suitable with the RTRW Surabaya, but due to the large sedimentation, there are some things that must be considered such as the uncertainty of land ownership arise in Kenjeran and ecosystem damage. The solution offered is that the government should restrict the use of arising land and there should be clarification of rules from the government on arising land. Keyword: Sedimentation, Morphological Changes, Kenjeran-Surabaya


Introduction
Coastal area is an area between land and sea, landward covering the land part, either dry or submerged, which is still affected by the nature of the sea such as tides, and sea breeze.Meanwhile towards the sea compromise of the sea that is still influenced by natural processes that occur on land such as sedimentation and fresh water current, or caused by human activities on land such as deforestation and pollution.
The sediment transport process is one of the main proccess in coastal areas.Sediment transport is a displacement of sediment material from a certain place to another.This move is in the form of inflow or outflow.If the outflow is more than the inflow then there will be erosion and vice versa if the outflow is less than the inflow then the accretion process occurs [1,2,3].Generally sediment transport movement is divided into three which is bed load, wash load and suspended load.Wash Load is very fine particles which are transported by the water, but those particles do not exist on the bed.Hence, wash load will not be considered.Suspended load is defined as part of the total transport load which is moving without continous contact with the bed as the result of the agitation of the fluid turbulence.The appearance of ripples will increase the bed shear stress (flow resistance) [2,3].On the other hand, more grains will be suspended due to the flow separation on the lee side of the ripples.Thus the suspended load is related to the total bed shear stress [3].Bed load is defined which has more or less continuous contact with the bed, the particles are simply rolling, trundle or small jumping at the bottom because of the relatively slow flow rate.Bed load sediment transport modelling under non-linier and irregular waves motion based on bottom shear stress model has been done by [4,5,6,7].One of the formulas used to calculate the bed load transport by using the DELFT 3D software in the present study is the Engelund Hansen formula [3], as follows S=Sb+Ss,eq =(0.05α q 5 )/(√g C 3 ∆ 2 D50 ) (1) Which is: q = flow velocity (m/s), ∆ = relative density, C = Chézy friction coefficient and α = Calibration coeficient.
As a result of changes in sediment's volume is the erosion, sedimentation, and arising land.Kenjeran is one of the coastal areas in Surabaya which become trading and service area, as well as tourism area.Therefore, research on coastal morphology changes in Kenjeran, becomes important because of many functions of spatial and population in this region.The results of this analysis can deliver recommendations in the development of Kenjeran area to improve the welfare of the community and reduce environmental problems.

Materials and Method
This research was conducted in three stages: data collection, hydrodynamics and sediment transport modelling using Delft 3D software and spatial study of Surabaya city.The data used include topographic and bathymetry maps, tidal data, sediment properties data, and Surabaya Spatial Plan [8,9].
Numerical modelling was included the meshing grid, the data input on flow and wave module, and the validation model [3].This modelling is made to analyze and predict sediment transport movement so that the coastal morphology changes can be seen.The results of this model will be used as a recommendation for the development of Surabaya city in accordance with Surabaya Spatial Plan [8].In addition, in this study, will also assess the suitability of conditions in the field with the plan by the government in Spatial Planning of Surabaya [8].

Result and Discussion
The location in this study was at Surabaya.Geographically located at coordinates 7 ° 14'00 '' SL (South Latitude) and 112 ° 47'02 "EL (East Longitude).The area reviewed in this study is Kenjeran-Surabaya with the given following data: 1.
Significant wave average (Hs): 0.45 meters For a more detailed explanation, the following observation points are selected: Based on the result of total transport model was obtained that the data of sedimentation rate in each take at each observation point, where the largest total transport value was occured at the observation point (233,326) as 3.48 x10 -9 m 3 /s/m and the lowest total transport value at the point of observation (280,314) that is 4.62 x10-11 m 3 /s/m.The results of sedimentation rate values at each observation point can be seen in Table 3 as follows: At the observation point (233,326) in Kelurahan Kedung Cowek, there was sedimentation of 7x10 -5 meters, as evidenced by the change of bed level from -5.6915 meters to -5.9615 meters and also the addition of sediment period from 8025 kg / m 2 to 8025.035 kg / m 2 as shown in Figure 1, Figure 2 and Figure 3.At observation point (280,314) in Kenjeran Sub-district sedimentation occurs 1x10 -3 meter, as evidenced by the change of bed level from -2.4337 meters to -2.4328 meters and also the addition of sediment period from 8025 kg / m 2 to 8025.45 kg / m 2 as shown in Figure 4, Figure 5 and Figure 6.At observation point (353,288) in Sukolilo Sub-district, sedimentation occurs 4x10 -3 meter, as evidenced by the change of bed level from -1.6345 meters to -1.6305 meters and also the addition of sediment period from 8025 kg / m 2 to 8026.8 kg / m 2 as shown in Figure 7, Figure 8 and Figure 9. From Tambak Wedi sub-district to Sukolilo sub-district there is extensive sedimentation, which is 2.3x10 6 m 2 area with sedimentation of 0.02 m and 7.5x10 6 m 2 with sedimentation of 0.1 m in the next 15 years based on the sediment transport modelling result as given in Figure 10.

Conclusion
Coastal in Tambak Wedi, Kenjeran and Sukolilo Sub-districts are dominated by sedimetation.The use of this area is in accordance with the Surabaya Urban Spatial Plans, but there are some things that must be done in the future development.Such as limiting the use of arising land in the residential areas of fishermen, conducting the development of environment-based tourism and supervise coastal environment from garbage.So that marine ecosystems are not damaged.

Table 1 .
Observation point location