Analysis of topographic parameters underpinning landslide occurrence in Kigezi highlands of southwestern Uganda

Abstract

An assessment of the influence of topography on landslide occurrence in the Kigezi highlands of southwestern Uganda was conducted. Whereas the frequency and magnitude of landslides in these highlands are on the increase, the topographic attributes underpinning landslide occurrence are not well understood. Sixty-five landslide scars were surveyed and mapped to produce landslide distribution maps. Specific topographic parameters, namely slope gradient, profile curvature, topographic wetness index (TWI), stream power index (SPI), and topographic position index (TPI), were assessed on landslide slope sites. The attributes were parameterized in the field and GIS environment using a 10-m DEM. Landslides were noted to concentrate along narrow topographic hollows, as opposed to broad concave slopes in the landscape. The occurrence is dominant in slope zones where slope gradient, profile curvature, TWI, TPI, and SPI are 25°–35°, 0.1–5, 8–18, − 1–1, and > 10, respectively. It was established that profile curvature and slope gradient are the most and least significant topographic parameters in landslide occurrence (R² = 0.802, p value = 0.088 and R² = 0.5665, p value = 0.057), respectively. An understanding of these topographic underpinnings would serve to identify and predict potential landslide zones within the landscape and enhance landslide hazard mitigation.

Appendix: Landslide scar geometric characteristics

Landslide scars	Landslide scar dimensions (m)			Area of the landslide scar (m2)	Volume of the scar (m3)	Gradient (°) range at slide failure zone
	Average width (m)	Average depth (m)	Length (m)
1	3.7	1.7	402	1487	2462	25–28
2	9.66	2.3	463.5	4477	6064	30–32
3	17.5	0.74	350	6125	4427	30–34
4	2.1	1.2	602	1264	3773	26–27
5	8.5	2.245	14.1	120	258	30–33
6	10	5	600	6000	30,000	33–35
7	10	5	400	4000	20,000	32–34
8	10	5.3	498	4980	26,394	31–33
9	16.6	4.3	315	5229	22,600	33–35
10	10	0.5	12.5	125	63	23–25
11	5.6	0.85	525.1	2941	1676	42–45
12	5.8	2.3	530	3074	10,508	39–42
13	2.7	1.8	885	2390	3669	33–36
14	3.14	1.52	786	2468	4341	30–33
15	2.95	1.6	784	2313	4518	34–37
16	6.2	2.8	835	5177	14,496	35–37
17	4.33	2.8	752	3256	9413	29–32
18	5	2.5	600	3000	7500	33–35
19	2.5	2.5	653	1633	4081	34–37
20	1.7	1.9	268	456	866	29–31
21	1.2	1.4	198	238	333	24–27
22	0.9	2.1	213	192	403	30–33
23	2.4	2	201	482	965	28–30
24	1.7	1.4	341	580	812	17–19
25	2.3	1.9	189	435	826	20–23
26	2.8	1.7	244	683	1161	26–29
27	1.9	1.2	196	372	447	31–34
28	2.4	1.5	204	490	734	15–18
29	2.8	1.9	302	846	1607	19–22
30	1.9	1.6	194	369	590	29–32
31	2.1	2	219	460	920	26–29
32	1.3	1.8	142	185	332	24–26
33	2.7	2.2	408	1102	2424	29–31
34	2.5	2	386	965	1930	34–37
35	1.6	0.9	125	200	180	26–29
36	1.7	2.1	184	313	657	20–23
37	2.4	2.2	296	710	1563	23–26
38	1.8	1.2	202	364	436	28–31
39	1.4	1.7	182	255	433	30–34
40	2.7	2.2	501	1353	2976	25–28
41	2.1	1.7	234	491	835	18–21
42	1.5	1.8	267	401	721	28–32
43	2.2	2.2	58	128	281	25–27
44	1.9	2.7	135	257	693	22–25
45	2.8	1.2	196	549	659	30–33
46	2.3	1.9	243	559	1062	28–31
47	4.2	0.9	55	231	208	26–30
48	2.9	1.1	129	374	412	33–35
49	3.2	0.7	231	739	517	29–32
50	3.1	0.8	89	276	221	20–22
51	2.8	2.1	197	552	1158	18–21
52	3.4	1.7	238	809	1376	17–19
53	3.2	1.2	345	1104	1325	32–34
54	2.8	0.8	118	330	264	16–18
55	1.8	1.1	102	184	202	18–20
56	3.6	2.8	189	680	1905	29–32
57	3.9	3.1	213	831	2575	25–28
58	3.2	2.7	96	307	829	27–29
59	1.8	1.2	47	85	102	22–25
60	1.2	0.8	66	79	63	20–22
61	5.9	2.1	138	814	1710	26–29
62	3.6	1.9	123	443	841	32–34
63	6.2	3.2	84	521	1667	29–32
64	7	1.7	73	511	869	23–25
65	4.2	1.3	144	605	786	27–30