Vulnerability assessment of flood-affected locations of Bangalore by using multi-criteria evaluation

Figures & data

Figure 1. Study area Bruhat Bangalore Mahanagara Palike (BBMP).

Table 1. Data source.

Type of data	Description	Source	Use
Flood locations	Reports on floods	BBMP office, newspapers, television news and web article	To prepare the GIS (flood) map based on post incidence
Cartosat-1 DEM	1ʺ arc generated from PAN (2.5 m) stereo data	National Remote Sensing Centre, Government of India, Hyderabad	Used to determine the morphometry and floodplains
LISS-III, date of pass	24 m resolution of Resourcesat-1, date of pass, Wednesday, 9 November 2011		Used for land-use classification and to determine urban impervious surface
Bangalore guide map	1:20,000 surveyed during 1960	Survey of India	Used to identify the existing lakes, lost lakes, lake encroachments, lost vegetable gardens, and marshy lands, and streams
Topographical map	1:25,000 surveyed during 1973–1974
Bangalore guide map	1:20,000 surveyed during 1979
Bangalore guide map	1:50,000 surveyed in 1998–2000.
The daily rainfall	From 1904 to 2013	District Statistical office of Bangalore	Rainfall dispersion analysis

Figure 2. Workflow diagram.

Table 2. Table showing percentage of different stream orders.

	No of streams	Total length of streams	Average length of streams	% of streams in number	% of streams in length
First order	2392	955,301	399	73.15	59.40
Second order	807	514,948	638	24.68	32.02
Third order	62	84,788	1368	1.90	5.27
Fourth order	5	32,206	6441	0.15	2.00
Fifth order	4	20,989	5247	0.12	1.31
Sum	3270	160,8231		100.00	100.00

Figure 3. Map showing flood-affected areas with streams.

Table 3. Table showing distribution of slopes based on IMSD, NRSA 1995 guidelines.

Type of terrain	Slope in %	% of area covered
Nearly level	0–1	13
Very gently sloping	1–3	45
Gently sloping	3–5	27
Moderately sloping	5–10	14
Strongly sloping	10–15	1
Moderately steep to steep sloping	15–30	0
Very steep sloping	>35	0

Figure 4. Map showing flood-affected areas with a slope.

Figure 5. Map showing flood-affected points with floodplains.

Figure 6. Map showing flood-affected points with urban developments in floodplains.

Figure 7. Map showing flood-affected points with lost lake database.

Figure 8: Map showing flood-affected points with the impervious surfaces.

Figure 9. Box plot showing the rainfall dispersion from 1904 to 2013.

Figure 10. Map showing the spatial variability of rainfall.

Figure 11. Map showing the variability of rainy days.

Table 4. Zone-wise flood locations.

		One time	Two times	Three times	Greater than three times
High-risk zone	49	39	5	1	4
		(39 × 1 = 39)	(5 × 2 = 10)	(1 × 3 = 3)	(4 × 3 + 5 × 1 = 17)
Moderate-risk zone	136	108	16	9	3
		(108 × 1 = 108)	(16 × 2 = 32)	(9 × 3 = 27)	(4 × 2 + 5 × 1 = 13)
Low-risk zone	68	59	7	1	1
		(59 × 1 = 59)	(7 × 2 = 14)	(1 × 3 = 3)	(1 × 4 = 4)
Safe zone	27	24	3	-	-
		(24 × 1 = 24)	(3 × 2 = 6)	-	-

Figure 12. Flood zone map.