Abstract

This project goes over 2 measurements observing Jakarta’s coastal changes and sea surface temperature (SST) changes over years regarding the issue of Jakarta sinking that been predicted by NASA. Remote sensing is a budget friendly and time effective method to observe land changes in a spacious area. Analysis for a better assessment on how urgently the government and the citizens need to implement a solution to maintain land while reducing global warming, considering that land sinking endangers most of the city’s population. To observe the changes in coastline, the ArcGis software is used to generate an image of coastlines of the same location from various years, which is done by processing the data obtained from earthexplorer.gov. While for SST changes, data from earthdata.nasa.gov processed in Seadas software, then quantified and mapped using ArcGis. An analysis and conclusion of the processed data is found in the sections below.

Introduction

News about the Jakarta sinking has been widespread due to the predictions that Jakarta will have sunk within this century, which is due to the rapid urbanization of the city causing a great burden of weight on the land, and land subsidence caused by the extraction of water from the ground, potentially signaling a threat for the lives of over 10 million people living in Jakarta (Ng, 2020). This phenomenon can be measured by comparing the coastlines of a certain location over a varying period of time, as this can be one way to reveal the change of the land’s position. Another factor to consider in the sinking of Jakarta is global warming and increasing Sea Surface Temperature (SST), which can be measured by seeing the change in SST over time. The factors of the Jakarta sinking are assessed in this project and analyzed to give a verdict on Jakarta’s sinking and how dangerous it is.

Materials to Remote Sensing

Satellite data: Landsat Collection and AQUA-Modis
ArcGis and SeaDas

Methods of Processing the Satellite Image

Processing the Landsat Satellite Image using ArcGis

Satellite Image Data Correction

Add data that have been downloaded before, one by one and choose the file that has Band 3 and Band 6 data. Band 3 captured land (green) and Band 6 is a SWIR (Short Wavelength Infrared) that captures a lot more high quality image. Correction was simply done in ArcGis using Raster Calculator > Float Function: float(“band3-band6)/float(“band3+band6). After this process, the basemap of Region in Indonesia shapefile is inserted. Then using an Image Analysis feature, clip the targeted area in the basemap. Correction was done again using Raster Calculator > Conditional Function: con(“clip_raster year”)<=0,1,0. This correction is done to perform a conditional if/else evaluation on each of the input cells of an input raster.

Coastal line tracing

After the correction process, the type of product will be called ‘raster.’ Then a conversion from raster to line should be done. The step is: raster to polygon then polygon to line. Now the image type had become a line. Right click on the line and click start editing to remove unnecessary part and tracing the coastal line.

Processing the AQUA-Modis Satellite Image using SeaDas

1.Open product in SeaDas software and choose on the downloaded SST data. In the layer box, click bands to show the SST image.

2.Using the color manipulation feature, choose the wanted color to represent the temperature distribution.

3.Right click on the image and press Spatial Subset from View and click on geo coordinates. Insert the wanted latitude and longitude based on the targeted area to lock the preview image on targeted area. After this, the cropped area is made in the new layer.

4.Open the new layer then use Rectangle drawing tool to select the area to be exported as quantified data consist of longitude, latitude and temperature. The file will be saved as .txt file.

5.Open the .txt file and do a correction by removing the NaN data or data which has no record.

6.To remapped theSST, insert the .txt corrected data to ArcGis in order to get a more high resolution image.

Conclusion and Future Work

Based on the result, it is visible that starting 2015 there is addition of land near the PIK area. The addition of land is commonly known as reclamation. Reclamation which the government agree to be built, provides more land for housing and infrastructure, reduces unused land, and provides protection from coastal erosion. Therefore, it also comes with negative consequences. It may lead to a loss of natural habitat and biodiversity or might caused ecosystem imbalance due to the sudden changes in the environment. It can also lead to a higher SST since the land construction and human activities that inhabit the land would release pollution to the air and waters. The new land now is almost fully developed along with the research done by NASA which stated that Jakarta predicted to be sinking by 2050. Creating a new land and constructing a huge walls are two projects that mean as an effort to prevent Jakarta from sinking. Therefore, artificial islands are often among the fastest types of land to subside because their sand and soils settle and become compacted over time. Satellites and ground-based sensors have recorded parts of North Jakarta subsiding by dozens of millimeters per year. On new artificial islands, that rate has soared as high as 80 millimeters per year. This reason is a red flag for Jakarta citizens since the risk is the inevitable sea level rise. Sea level rise is highly correlated with global warming that caused ice melted on the North and South pole. So it is very urgent for the government and us as a citizens to do something to maintain our environment to slower the climate change rate which also correlated to slower the sinking of Jakarta as well.

It is important for people (not only the government but also citizens) in Jakarta to take action in maintaining the new land by reducing activities that might negatively impacted the climate. installing water pipes throughout the city, reducing some concrete off the ground to expose the land to rainwater, limiting the use of too much electricity, reducing vehicles that emit pollution and recycling. Hopefully, the Indonesian government and citizens can also implement a solution to stop the city from completely sinking, though time is running out.

Jonathan Viscardy Tjia

PUBLICATION AND PRESENTATION

EVENTS ATTENDED