Remote-sensing perspective and GPR subsurface perception on the growth of a recently emerged spit at Talashil coast, west coast of India

Figures & data

Figure 1. Location map of the Talashil spit, Malvan coast, west coast of India.

Source: Google Earth: image@Digital Globe.

Figure 2. Historical evolution of the Talashil spit from 1973 to 2013. (a) Landsat MSS dated 26-01-1973; (b) Landsat TM 04-02-1989; (c) Landsat TM 14-11-1999; (d) Landsat TM 17-01-2002; (e) IRS P6 07-02-2006; and (f) Digital Globe image (Google Earth) 04-05-2013.

Figure 3. Conceptual sketch on the various stages of formation of Talashil spit; (a1) and (a2) emergence of submerged shoal; (b1) main land with submerged shoals, (b2) sand bar extension and (b3) spit growth. (1) Main land; (2) river; (3) sea; (4) sandbar; (5) river islands; (6) submerged shoals; (7) extended sandbar; (8) submerged river islands near to extended sandbar; and (9) grownup spit.

Figure 4. Decadal growth of the spit from 2003 to 2013. (a1) satellite image of 2003; (b1) 2009; (c1) 2011; (d1) 2012; (e1) 2013; and (a2)–(e2) sketches of the spit boundary with respect to years.

Source: Google Earth: image@Digital Globe.

Table 1. Area and perimeter of the spit in various years from 2003 to 2013.

	Area		Perimeter		Activity
Year of imagery	Area (km^2)	Difference (km^2)	Perimeter (km)	Difference (km)
December 2003	0.300	–	2.50	–	–
March 2009	0.295	−0.004	2.49	−0.01	Erosion
March 2011	0.307	0.012	2.51	0.02	Accretion
January 2012	0.313	0.006	2.52	0.01	Accretion
May 2013	0.308	−0.004	2.51	−0.01	Erosion
Decadal change (2003 to 2013)
December 2003	0.300	–	2.50	–	–
May 2013	0.308	0.008	2.51	0.01	Accretion

Figure 5. Changes in geomorphic features in 2003 and 2013. (1) Sea shore; (2) dune area; (3a and b) swampy micro-enclosures; (4) lowland; and (5) main land.

Figure 6. Erosion and accretion locations/zones with reference to different years. (a) Boundary layers of 2003–2009; (b) 2009–2011; (c) 2011–2012; (d) 2012–2013; and (e) 2003–2013.

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Table 2. Comparison of accretion and erosion from 2003 to 2013 period.

Years	Accretion (km^2)	Erosion (km^2)	Difference (km^2)	Years	Activity
2003–2009	0.021	0.026	−0.005	6	Erosion
2009–2011	0.023	0.009	0.014	2	Accretion
2011–2012	0.010	0.004	0.006	1	Accretion
2012–2013	0.027	0.006	0.021	1	Accretion
Total	0.081	0.045	0.036	–	–

Table 3. Areas under erosion and accretion in the spit at various years (2003–2013).

Map reference	Years	Location	Area (km^2)	Year-wise area (km^2)	Total (km^2)
Accretion
a	2003–2009	A1	0.200	0.021	0.081
		A4	0.001
b	2009–2011	B1	0.002	0.024
		B3	0.020
		B5	0.002
c	2011–2012	C1	0.003	0.010
		C3	0.003
		C5	0.004
d	2012–2013	D1	0.024	0.027
		D3	0.003
		D6	0.001
e	2003–2013	E1	0.040	0.041	–
		E3	0.001
Erosion
a	2003–2009	A2	0.023	0.026	0.045
		A3	0.003
b	2009–2011	B2	0.005	0.009
		B4	0.002
		B6	0.003
c	2011–2012	C2	0.001	0.004
		C4	0.002
		C6	0.001
d	2012–2013	D2	0.001	0.006
		D4	0.003
		D5	0.002
e	2003–2013	E2	0.033	0.033	–

Figure 7. (a) Comparison of erosion and accretion (2003 to 2013); (b) locations of reverse dynamics around the spit.

Figure 8. Boundary comparison (2003–2013) of Talashil spit.

Source: Google Earth: image@Digital Globe.

Figure 9. Time domain GPR profile illustrating various subsurface features. (1a) Saturated bottom bed set layers; (1b) compact sand layers; (2) erosional surface; (3) cyclic erosion and accretion zone (unconsolidated upper sand layers); (4) paleo-levee; (5) discontinuity; (6) vertically titled sand layers; (7) dune zone – bottom sand layers; (8) dune zone – upper sand layers; and (9) inter-tidal zone (saturated).