Geoinformation for Urban Planning and Adaptation to Climate Change (GPAC), Bangladesh
Report of the project:
Forced by the climate change, the people in Bangladesh migrate to the cities. Therefore, the demand for safe and cheap building ground is very high. To react on this, the cities are growing vertically and also laterally. Planners and decision makers demand a climate-resilient urban planning including sub-ground condition data and geodata that are reliable and easy-understandable.
The project areas are in Faridpur, Satkhira, Barisal, Khulna, Kushtia and Sirajganj.
Location of the project cities in Bangladesh
Source: BGR
The project goals are:
- Strengthening of the direct partner GSB (Geological Survey of Bangladesh) in its role as the governmental service provider for urban planners and decision makers
- Strengthening of urban planners and decision makers in the use of geodata
- Enhancement of the cooperation between the GSB and the users of its geodata.
The BGR working group on remote sensing supports the project with the integration of remote sensing methods for analyzing multispectral satellite data (Sentinel-2 and Landsat) and radar data (Sentinel-1 and TerraSAR-X). Land-use classifications provide spatial change information on the expansion of urban areas and shifting river courses. The shifting direction of the rivers can be an indicator for the estimation of erosion-prone areas. Finally, ground motion maps derived from radar data are used to identify stable areas that are suited as building ground.
Partner personnel is supported in the application of remote sensing methods, data documentation and reporting. The professional instruction of colleagues by the trained partner personnel and the provision of user-orientated consulting are the overall goals.
Use of Sentinel-1 based geodata
Due to their high temporal resolution and spatial coverage, Copernicus Sentinel-1 data is particularly well suited for the mapping of ground motion and flooding events in the Bangladeshi project areas. The free data availability will encourage the project partner, the Geological Survey of Bangladesh (GSB), and the urban planners to update the Copernicus-based products regularly and incorporate them into their planning processes.
- Ground motion monitoring with radar interferometry (InSAR)
Multi-temporal radar interferometry (InSAR) techniques such as Persistent Scatterer Interferometry (PSI) or Small Baseline Subset (SBAS) allow the extraction of ground motion information from radar images. Data archives of freely available radar data go back to the 1990s for large parts of the Earth. With the launch of the Copernicus Sentinel-1 satellites starting in 2014, radar data are available with a repeat frequency of a few days for the entire world. This high data quality and availability enables large-scale and multi-temporal analyses of ground motion dynamics with a high temporal and spatial density and millimeter-scale accuracies (see Fig.1).
Figure 1: Vertical movement patterns for the Faridpur project area (10/2014-12/2019)
Source: BGR
Within the Geo-Information for Urban Planning and Adaptation to Climate Change project, both PSI and SBAS are used for ground motion analyses in several project areas. Exemplary workflows for the systematic integration of multi-temporal InSAR data into a climate change-adapted urban planning in Bangladesh are being established at the project sites. The ground motion data enables the identification and - together with other relevant geospatial data – characterization, of potential building ground as well as the monitoring of individual buildings and infrastructure elements. In addition, the data can be used to model future flooding scenarios.
- Inundation Mapping
Figure 2: Number of monsoonal flooding events (green: 1-2, red: 3-4, blue: 5-6) in Bangladesh between 2015 and 2020 based on Copernicus Sentinel-1 data
Source: BGR
Due to its low-lying geographic location in the delta of the Ganges River and the prevailing monsoon climate, Bangladesh is affected by high-dynamic annual flooding events.
Copernicus Sentinel-1 data enables the detection and visualization of peak flood levels. The extent and the frequency of inundation can be analyzed on a nationwide scale due to the high temporal resolution of the data (repeat frequency of 6-12 days) (see Fig. 2).
On the local level, these geodata can help to estimate the inundation hazard of urban development sites.
With the free and continuous availability of satellite data from the Copernicus program, the analysis can be updated regularly and gains significance. Together with a processing using free-of-charge software and the training of specialists, a sustainable and future-proof application can be provided.
Literature: