Abstract
The Danube and its islands play a pivotal role in maintaining the ecosystem balance in the region. Anthropogenic activities over the past century, combined with extreme natural events, such as floods, interact in synergy and can significantly influence the dynamics of the islands. This includes the appearance or disappearance of islands, changes in their surface area, length, shape, number, and so forth. The objective of this work is to catalogue, study, and monitor the evolution of islands within a 445.29 km stretch of the Lower Danube River, between Orşova and Vedea. These are two Romanian localities situated at the confluence with the Cerna and Vedea rivers, respectively. For this study, we utilized SAR (Synthetic Aperture Radar) images captured on various dates to identify the existing islands. After mapping each island and sub-island, we calculated their respective morphometric parameters and compared them. The results reveal a decrease of 12 islands and/or sub-islands, resulting in a total of 74 islands identified in 2022 with a combined area of 147.63 km2, in contrast to 86 in 1992 with a total area of 154.29 km2. Over this 30-year span, we have estimated an average reduction rate of approximately 0.22 km2/year, with an annual “de-sedimentation” rate of around 0.14%. This accelerated dynamic stems from extreme meteorological events, exacerbated by human activities, amplifying the hydromorphological processes—especially in areas sensitive to water level variations, slope fluctuations, and “de-sedimentation”.
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Acknowledgements
We thank the European Space Agency (ESA) for providing us with the SAR images of the ERS and Sentinel 1 satellites as part of a research project on the monitoring and surveillance of the Danube islands in the Orşova–Vedea sector, Romania. We also thank the Professor Florin TATUI, from the University of Bucharest for proofreading this article. We are grateful to the National Meteorological Administration of Romania and more especially to Dr. Alexandru DUMITRESCU (Department of Climatology) for the meteorological data.
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KH conceived the idea presented, described the methodology adopted, performed the image processing and numerical calculations and took the initiative to write the manuscript. FG designed the general idea, helped supervise the project, organized the design and implementation of the research, and wrote part of the manuscript. ZN helped describe the methodology adopted and performed the verification and analysis of the results. AEO carried out the bibliographic study, performed the verification and analysis of the results, and helped and wrote part of the manuscript. YA processed and produced the maps. All authors contributed to the interpretation of the results and contributed to the final manuscript. All authors have read, understood, and have complied as applicable with the statement on “Ethical responsibilities of Authors” as found in the Instructions for Authors and are aware that with minor exceptions, no changes can be made to authorship once the paper is submitted.
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Appendices
Appendix 1: Table showing the morphometric parameters of all islands/sub-islands extracted in 1992 and 2022 on the Orşova–Vedea section and their differences
No | Name of Island | 1992 | 2022 | 2022–1992 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Coordinate of centroid | Perimeter | Area | Coordinate of centroid | Perimeter | Area | Coordinate of centroid | Perimeter | Area | |||||
Lon (°) | Lat (°) | P (m) | S (m2) | Lon (°) | Lat (°) | P (m) | S (m2) | ∆Lon (°) | ∆Lat (°) | ∆P (m) | ∆S (m2) | ||
1 | Island_1 | 22.55 | 44.66 | 3099.27 | 271,591.99 | 22.55 | 44.66 | 3197.17 | 270,841.7 | 0 | 0 | 97.9 | − 750.29 |
2 | Island_2_1 | 22.69 | 44.61 | 3669.27 | 555,421.03 | 22.69 | 44.61 | 3474.8 | 539,019.17 | 0 | 0 | − 194.47 | − 16,401.9 |
3 | Island_2_2 | 22.7 | 44.6 | 2395.24 | 117,703.27 | 22.71 | 44.6 | 2450.31 | 124,996.53 | 0.01 | 0 | 55.07 | 7293.26 |
4 | Island_3 | 0 | 0 | 0 | 0 | 22.69 | 44.52 | 1615.83 | 99,614.39 | 22.69 | 44.52 | 1615.83 | 99,614.39 |
5 | Island_4 | 22.54 | 44.36 | 34,558.9 | 23,547,804 | 22.54 | 44.36 | 34,378.3 | 23,522,108 | 0 | 0 | − 180.6 | − 25,696.5 |
6 | Island_5 | 22.65 | 44.29 | 2681.74 | 171,843.84 | 0 | 0 | 0 | 0 | − 22.65 | − 44.29 | − 2681.74 | − 171,844 |
7 | Island_6_1 | 22.76 | 44.2 | 4497.28 | 857,824.3 | 22.76 | 44.2 | 3669.29 | 687,662.67 | 0 | 0 | − 827.99 | − 170,162 |
8 | Island_6_2 | 22.75 | 44.2 | 1874.3 | 153,955.53 | 22.75 | 44.2 | 772.37 | 17,701.65 | 0 | 0 | − 1101.93 | − 136,254 |
9 | Island_6_3 | 22.75 | 44.2 | 1308.04 | 43,971.86 | 22.75 | 44.2 | 530.7 | 12,016.15 | 0 | 0 | − 777.34 | − 31,955.7 |
10 | Island_7_1 | 22.85 | 44.15 | 7885.89 | 1,102,038.5 | 22.86 | 44.14 | 2699.49 | 174,670.7 | 0.01 | − 0.01 | − 5186.4 | − 927,368 |
11 | Island_7_2 | 22.84 | 44.14 | 2441.22 | 151,089.01 | 22.85 | 44.14 | 2054.66 | 130,907.52 | 0.01 | 0 | − 386.56 | − 20,181.5 |
12 | Island_8 | 22.89 | 44.11 | 1904.18 | 128,598.49 | 22.89 | 44.11 | 2016.5 | 138,927.67 | 0 | 0 | 112.32 | 10,329.18 |
13 | Island_9 | 23.03 | 44.06 | 4284.03 | 490,338.61 | 23.04 | 44.06 | 5204.76 | 503,923.88 | 0.01 | 0 | 920.73 | 13,585.27 |
14 | Island_10_1 | 22.99 | 44.01 | 7021.75 | 1,177,018.5 | 22.99 | 44.01 | 6321.8 | 1,145,597.6 | 0 | 0 | − 699.95 | − 31,420.9 |
15 | Island_10_2 | 22.97 | 44.01 | 1496.38 | 83,447.75 | 22.96 | 44.01 | 2003.63 | 158,238.44 | − 0.01 | 0 | 507.25 | 74,790.69 |
16 | Island_10_3 | 22.96 | 44.01 | 2978.74 | 366,653.96 | 22.95 | 44.01 | 1116.33 | 52,055.44 | − 0.01 | 0 | − 1862.41 | − 314,599 |
17 | Island_10_4 | 22.95 | 44.01 | 1343.67 | 58,024.31 | 22.94 | 44.01 | 703.14 | 21,211.4 | − 0.01 | 0 | − 640.53 | − 36,812.9 |
18 | Island_10_5 | 22.94 | 44.01 | 1215.9 | 41,108.95 | 0 | 0 | 0 | 0 | − 22.94 | − 44.01 | − 1215.9 | − 41,109 |
19 | Island_11_1 | 22.89 | 43.98 | 8756.12 | 2,333,982 | 22.89 | 43.98 | 8556.52 | 2,311,524.6 | 0 | 0 | − 199.6 | − 22,457.5 |
20 | Island_11_2 | 22.89 | 43.99 | 1451.38 | 59,629.94 | 22.89 | 43.98 | 1094.32 | 41,274.72 | 0 | − 0.01 | − 357.06 | − 18,355.2 |
21 | Island_12_1 | 22.85 | 43.92 | 5391.81 | 1,257,059 | 22.85 | 43.92 | 5412.86 | 1,287,885.6 | 0 | 0 | 21.05 | 30,826.67 |
22 | Island_12_2 | 22.86 | 43.92 | 1250.5 | 59,646.24 | 0 | 0 | 0 | 0 | − 22.86 | − 43.92 | − 1250.5 | − 59,646.2 |
23 | Island_13_1 | 22.83 | 43.88 | 4345.61 | 479,216.63 | 22.83 | 43.88 | 4379.41 | 447,357.53 | 0 | 0 | 33.8 | − 31,859.1 |
24 | Island_13_2 | 22.84 | 43.87 | 3015.55 | 236,877.61 | 22.84 | 43.87 | 2953.35 | 226,299.29 | 0 | 0 | − 62.2 | − 10,578.3 |
25 | Island_14_1 | 23.03 | 43.79 | 9145.45 | 1,385,287.7 | 23.02 | 43.79 | 11,909.23 | 1,809,557.2 | − 0.01 | 0 | 2763.78 | 424,269.5 |
26 | Island_14_2 | 23.05 | 43.8 | 5429.19 | 763,022.36 | 23.06 | 43.8 | 5427.5 | 708,247.38 | 0.01 | 0 | − 1.69 | − 54,775 |
27 | Island_14_3 | 23.01 | 43.8 | 8782.8 | 1,003,309.6 | 23.01 | 43.8 | 8887.65 | 1,017,461.7 | 0 | 0 | 104.85 | 14,152.13 |
28 | Island_14_4 | 22.96 | 43.81 | 4031.85 | 340,886.1 | 22.96 | 43.81 | 5368.21 | 520,928.46 | 0 | 0 | 1336.36 | 180,042.4 |
29 | Island_14_5 | 22.96 | 43.82 | 4767.99 | 485,328.86 | 22.96 | 43.82 | 4904.18 | 569,295.49 | 0 | 0 | 136.19 | 83,966.63 |
30 | Island_15_1 | 23.14 | 43.81 | 2273.79 | 175,799.1 | 23.14 | 43.81 | 2191.52 | 164,069.13 | 0 | 0 | − 82.27 | − 11,730 |
31 | Island_15_2 | 23.15 | 43.81 | 1765.77 | 45,922.2 | 23.15 | 43.81 | 1505.45 | 33,234.69 | 0 | 0 | − 260.32 | − 12,687.5 |
32 | Island_15_3 | 0 | 0 | 0 | 0 | 23.12 | 43.81 | 3391.03 | 221,908.52 | 23.12 | 43.81 | 3391.03 | 221,908.5 |
33 | Island_16_1 | 23.3 | 43.85 | 5739.89 | 1,079,615.6 | 23.3 | 43.85 | 6368.03 | 1,159,213.5 | 0 | 0 | 628.14 | 79,597.88 |
34 | Island_16_2 | 23.23 | 43.84 | 1325 | 52,340.7 | 23.23 | 43.84 | 1280.37 | 52,301.33 | 0 | 0 | − 44.63 | − 39.37 |
35 | Island_16_3 | 0 | 0 | 0 | 0 | 23.21 | 43.83 | 1319.23 | 65,650.33 | 23.21 | 43.83 | 1319.23 | 65,650.33 |
36 | Island_17_1 | 23.52 | 43.83 | 6709.62 | 1,245,812.7 | 23.52 | 43.83 | 7859.18 | 1,428,006.7 | 0 | 0 | 1149.56 | 182,194 |
37 | Island_17_2 | 23.56 | 43.81 | 3701.24 | 393,355.64 | 23.56 | 43.81 | 5250.02 | 690,025.04 | 0 | 0 | 1548.78 | 296,669.4 |
38 | Island_17_3 | 23.58 | 43.8 | 2878.05 | 254,608.48 | 23.59 | 43.8 | 5541.85 | 1,000,396.8 | 0.01 | 0 | 2663.8 | 745,788.4 |
39 | Island_18_1 | 23.74 | 43.79 | 24,490.91 | 9,051,666.9 | 23.74 | 43.79 | 24,505.8 | 9,069,263.3 | 0 | 0 | 14.89 | 17,596.45 |
40 | Island_18_2 | 23.78 | 43.79 | 11,392.75 | 4,595,475.5 | 23.78 | 43.79 | 10,310.71 | 4,292,973.8 | 0 | 0 | − 1082.04 | − 302,502 |
41 | Island_18_3 | 23.9 | 43.75 | 4571.02 | 481,919.79 | 23.9 | 43.75 | 4038.09 | 371,574.9 | 0 | 0 | − 532.93 | − 110,345 |
42 | Island_19_1 | 24.11 | 43.71 | 11,395.94 | 4,270,325.6 | 24.11 | 43.71 | 11,321.15 | 3,890,244.3 | 0 | 0 | − 74.79 | − 380,081 |
43 | Island_19_2 | 24.04 | 43.72 | 8199.18 | 1,546,212.7 | 24.04 | 43.72 | 8509.89 | 1,433,650.9 | 0 | 0 | 310.71 | − 112,562 |
44 | Island_19_3 | 24.08 | 43.71 | 1423.49 | 100,089.98 | 24.08 | 43.71 | 2303.31 | 187,664.89 | 0 | 0 | 879.82 | 87,574.91 |
45 | Island_20_1 | 24.32 | 43.7 | 6919.94 | 1,119,419.4 | 24.33 | 43.7 | 5733.74 | 875,930.01 | 0.01 | 0 | − 1186.2 | − 243,489 |
46 | Island_20_2 | 24.38 | 43.72 | 2473.53 | 115,007.09 | 24.38 | 43.72 | 1710.23 | 66,657.14 | 0 | 0 | − 763.3 | − 48,350 |
47 | Island_20_3 | 24.24 | 43.69 | 2779.6 | 121,332.01 | 0 | 0 | 0 | 0 | − 24.24 | − 43.69 | − 2779.6 | − 121,332 |
48 | Island_21_1 | 24.54 | 43.77 | 6900.87 | 1,471,399.1 | 24.54 | 43.76 | 6431.51 | 1,264,721.9 | 0 | − 0.01 | − 469.36 | − 206,677 |
49 | Island_21_2 | 24.52 | 43.76 | 3085.85 | 426,364.89 | 24.5 | 43.77 | 4480.05 | 386,648.64 | − 0.02 | 0.01 | 1394.2 | − 39,716.3 |
50 | Island_21_3 | 24.5 | 43.76 | 3753.52 | 383,617.8 | 24.52 | 43.76 | 1415.9 | 70,085.13 | 0.02 | 0 | − 2337.62 | − 313,533 |
51 | Island_21_4 | 24.54 | 43.76 | 3335.17 | 322,226.89 | 24.55 | 43.76 | 4740.16 | 320,079.98 | 0.01 | 0 | 1404.99 | − 2146.91 |
52 | Island_21_5 | 24.49 | 43.75 | 1372.93 | 76,195.65 | 0 | 0 | 0 | 0 | − 24.49 | − 43.75 | − 1372.93 | − 76,195.7 |
53 | Island_22_1 | 24.73 | 43.7 | 20,474.07 | 10,412,411 | 24.73 | 43.7 | 20,137.74 | 10,059,135 | 0 | 0 | − 336.33 | − 353,276 |
54 | Island_22_2 | 24.67 | 43.72 | 3047.09 | 391,216.45 | 24.64 | 43.74 | 5161.17 | 850,493.13 | − 0.03 | 0.02 | 2114.08 | 459,276.7 |
55 | Island_22_3 | 24.64 | 43.74 | 5450.98 | 837,424.8 | 24.71 | 43.71 | 2221.67 | 158,568.87 | 0.07 | − 0.03 | − 3229.31 | − 678,856 |
56 | Island_22_4 | 24.71 | 43.71 | 3588.1 | 259,986.66 | 0 | 0 | 0 | 0 | − 24.71 | − 43.71 | − 3588.1 | − 259,987 |
57 | Island_22_5 | 24.85 | 43.7 | 2183.36 | 149,240.65 | 0 | 0 | 0 | 0 | − 24.85 | − 43.7 | − 2183.36 | − 149,241 |
58 | Island_23_1 | 25 | 43.72 | 6886.78 | 2,100,768.4 | 25 | 43.72 | 6469.42 | 1,847,297.7 | 0 | 0 | − 417.36 | − 253,471 |
59 | Island_23_2 | 25.02 | 43.72 | 2940.02 | 374,030.77 | 25.02 | 43.72 | 2594.51 | 278,394.37 | 0 | 0 | − 345.51 | − 95,636.4 |
60 | Island_23_3 | 24.97 | 43.72 | 4766.23 | 744,921.79 | 24.97 | 43.72 | 4275.48 | 700,914.26 | 0 | 0 | − 490.75 | − 44,007.5 |
61 | Island_23_4 | 24.95 | 43.71 | 4224.07 | 446,856.99 | 24.95 | 43.71 | 4533.89 | 492,972.54 | 0 | 0 | 309.82 | 46,115.55 |
62 | Island_23_5 | 25.01 | 43.71 | 1774.49 | 112,631.07 | 25.01 | 43.71 | 887.49 | 39,210.25 | 0 | 0 | − 887 | − 73,420.8 |
63 | Island_23_6 | 25.02 | 43.71 | 3619.94 | 614,935.9 | 25.01 | 43.71 | 9673.22 | 891,597.61 | − 0.01 | 0 | 6053.28 | 276,661.7 |
64 | Island_23_7 | 25 | 43.71 | 2394.36 | 177,713.73 | 25.04 | 43.7 | 1648.64 | 73,039.98 | 0.04 | − 0.01 | − 745.72 | − 104,674 |
65 | Island_23_8 | 25.03 | 43.7 | 2047.38 | 150,311.68 | 0 | 0 | 0 | 0 | − 25.03 | − 43.7 | − 2047.38 | − 150,312 |
66 | Island_23_9 | 24.96 | 43.72 | 864.54 | 38,600.99 | 0 | 0 | 0 | 0 | − 24.96 | − 43.72 | − 864.54 | − 38,601 |
67 | Island_24_1 | 25.19 | 43.67 | 34,569.33 | 50,650,396 | 25.19 | 43.67 | 32,980.67 | 50,042,485 | 0 | 0 | − 1588.66 | − 607,911 |
68 | Island_24_2 | 25.16 | 43.65 | 7385.58 | 1,933,646.5 | 25.16 | 43.64 | 7208.44 | 1,864,876.1 | 0 | − 0.01 | − 177.14 | − 68,770.4 |
69 | Island_24_3 | 25.24 | 43.65 | 5205.66 | 732,347.16 | 25.24 | 43.65 | 4789.08 | 706,077.84 | 0 | 0 | − 416.58 | − 26,269.3 |
70 | Island_24_4 | 25.26 | 43.68 | 5180.36 | 664,557.14 | 25.27 | 43.67 | 6262.91 | 940,523.79 | 0.01 | − 0.01 | 1082.55 | 275,966.7 |
71 | Island_24_5 | 25.19 | 43.69 | 4789.96 | 521,261.98 | 25.19 | 43.69 | 4358.13 | 473,662.15 | 0 | 0 | − 431.83 | -47,599.8 |
72 | Island_24_6 | 25.16 | 43.7 | 2753.92 | 241,977.97 | 25.12 | 43.66 | 4988.94 | 625,726.81 | − 0.04 | − 0.04 | 2235.02 | 383,748.8 |
73 | Island_24_7 | 25.15 | 43.7 | 1854.67 | 128,761.61 | 0 | 0 | 0 | 0 | − 25.15 | − 43.7 | − 1854.67 | − 128,762 |
74 | Island_24_8 | 25.14 | 43.69 | 2179.4 | 220,066.52 | 0 | 0 | 0 | 0 | − 25.14 | − 43.69 | − 2179.4 | − 220,067 |
75 | Island_24_9 | 25.15 | 43.7 | 1528.79 | 63,662.2 | 0 | 0 | 0 | 0 | − 25.15 | − 43.7 | − 1528.79 | − 63,662.2 |
76 | Island_24_10 | 25.12 | 43.66 | 4301.59 | 555,129.64 | 0 | 0 | 0 | 0 | − 25.12 | − 43.66 | − 4301.59 | − 555,130 |
77 | Island_24_11 | 25.12 | 43.67 | 832.75 | 28,071.85 | 0 | 0 | 0 | 0 | − 25.12 | − 43.67 | − 832.75 | − 28,071.9 |
78 | Island_25_1 | 25.48 | 43.63 | 12,732.13 | 6,832,603.1 | 25.48 | 43.63 | 12,878.59 | 6,643,674.2 | 0 | 0 | 146.46 | − 188,929 |
79 | Island_25_2 | 25.54 | 43.65 | 5282.19 | 1,009,755.7 | 25.53 | 43.65 | 4182.39 | 646,120.58 | − 0.01 | 0 | − 1099.8 | − 363,635 |
80 | Island_25_3 | 25.5 | 43.64 | 4000.89 | 427,979.81 | 25.56 | 43.64 | 1179.44 | 40,271.17 | 0.06 | 0 | − 2821.45 | − 387,709 |
81 | Island_25_4 | 25.49 | 43.64 | 4246.43 | 355,563.1 | 25.51 | 43.64 | 1986.43 | 49,822.4 | 0.02 | 0 | − 2260 | − 305,741 |
82 | Island_25_5 | 25.56 | 43.64 | 1879.45 | 113,981.52 | 25.5 | 43.63 | 772.5 | 28,521.56 | − 0.06 | − 0.01 | − 1106.95 | − 85,460 |
83 | Island_25_6 | 25.57 | 43.65 | 4131.24 | 528,002.85 | 0 | 0 | 0 | 0 | − 25.57 | − 43.65 | − 4131.24 | − 528,003 |
84 | Island_25_7 | 25.58 | 43.66 | 2022.84 | 197,525.04 | 0 | 0 | 0 | 0 | − 25.58 | − 43.66 | − 2022.84 | − 197,525 |
85 | Island_25_8 | 25.5 | 43.63 | 560.05 | 21,554.98 | 0 | 0 | 0 | 0 | − 25.5 | − 43.63 | − 560.05 | − 21,555 |
86 | Island_26_1 | 25.68 | 43.68 | 15,456.16 | 6,707,367.1 | 25.68 | 43.68 | 15,391.49 | 6,116,377.5 | 0 | 0 | − 64.67 | − 590,990 |
87 | Island_26_2 | 25.66 | 43.68 | 2286.64 | 219,444.88 | 25.66 | 43.68 | 2096.72 | 163,295.19 | 0 | 0 | − 189.92 | − 56,149.7 |
88 | Island_26_3 | 25.66 | 43.67 | 2217.45 | 154,739.01 | 25.66 | 43.67 | 1573.02 | 107,121.63 | 0 | 0 | − 644.43 | − 47,617.4 |
89 | Island_26_4 | 25.77 | 43.71 | 2021.1 | 121,808.04 | 25.77 | 43.71 | 2570.86 | 134,015.09 | 0 | 0 | 549.76 | 12,207.05 |
90 | Island_26_5 | 0 | 0 | 0 | 0 | 25.76 | 43.71 | 2158.5 | 55,896.94 | 25.76 | 43.71 | 2158.5 | 55,896.94 |
91 | Island_26_6 | 0 | 0 | 0 | 0 | 25.76 | 43.71 | 499.52 | 11,989.27 | 25.76 | 43.71 | 499.52 | 11,989.27 |
Appendix 2: Comparison graphs of the perimeters (P) of the islands and sub-islands of the Danube River along Orşova–Vedea sector (study area), in 1992 and in 2022
Appendix 3: Comparison graphs of the areas (S) of the islands and sub-islands of the Danube River along Orşova–Vedea sector (study area), in 1992 and in 2022
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Hachemi, K., Grecu, F., Nougrara, Z. et al. Monitoring the dynamics of the Danube islands system, using SAR imagery (Orșova–Vedea sector, 1992–2022). Environ Earth Sci 82, 590 (2023). https://doi.org/10.1007/s12665-023-11281-8
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DOI: https://doi.org/10.1007/s12665-023-11281-8