Assessing land use /cover variation effects on flood intensity via hydraulic simulations

Figures & data

Figure 1. Field photographs (A) destroyed house (B) flood lines inside a house.

Figure 2. Study area location. Source: Author.

Table 1. Tillouguite station’ description.

Station name	No IRE	Coordinates			Measuring period
		X	Y	Z
Tillouguite	138/46	422,674	158,474	1100	1977–2017

Figure 3. Land use/cover annual evolution since October 1987 to 2017. Source: Geographic information system (QGIS) Open source.

Figure 4. Land use /cover rate evolution according to instantaneous flow peak and maximum monthly rainfall per year since 1987.

Table 2. Alfet watershed general characteristics.

General parameters
Area (km²)	66.81	Difference in height (m)	1404
Perimeter (km)	39.29	Slope (%)	6.77
Length (km)	20.73	Equivalent length (km)	15.48
Maximum elevation	2527	Equivalent length (km)	4.32
Minimum elevation	1123	IC Gravelius	1.36
X, Y outlet (m)	306 786	Concentration time Tc (min)	274.37
	147 382

Figure 5. Monthly rainfall graphic representation according to Normal low.

Table 3. Distributions low comparison criteria.

Model	Nb param	XT	P(Mi)	P(Mi|x)	BIC	AIC
Normal (maximum likelihood)	2	619.14	12.50	39.35	356.17	353.51
Weibull (maximum likelihood)	2	636.25	12.50	34.19	356.45	353.79
Pearson type 3 (maximum likelihood)	3	638.22	12.50	10.95	358.73	354.73
Gamma (method of moments)	2	688.73	12.50	10.33	358.85	356.18
Gumbel (method of moments)	2	721.58	12.50	4.20	360.65	357.98
Lognormal (maximum likelihood)	2	920.79	12.50	0.97	363.58	360.91
Inverse gamma (maximum likelihood)	2	1449.74	12.50	0.01	372.72	370.06
Exponential (maximum likelihood)	2	1326.10	12.50	0.00	377.75	375.09

Table 4. Precipitation statistical adjustment results by normal low.

Return period	Probability	Estimated precipitation	Standard	Confidence interval
100	0.9900	619.14	46.644	498.97–739.30
50	0.9800	584.66	42.682	474.70–694.62
20	0.950	532.93	37.060	437.45–628.40
10	0.9000	486.95	32.530	403.14–570.75
5	0.8000	431.26	27.951	359.25–503.26
2	0.5000	324.82	23.905	263.23–386.40

Table 5. Flow results according to different recurrences times.

Flow point m^3/s used in simulation
Recurrences time	Q(02)	Q(05)	Q(10)	Q(20)	Q(50)	Q(100)
Alfet river	72.84	96.46	112.05	116.46	143.51	166.72

Table 6. Extract from the simulation table results.

Profil	Year of return	Q total (m^3/s)	Min Ch. El. (m)	W.S. Elev. (m)	Water Elev. (m)	Water speed (m/s)	Flow area (m^2)	Top width (m)	Froude Chl.
1	100 year	166.72	1181.7	1183.66	1.96	3.34	49.92	44.35	1
2	100 year	166.72	1179.99	1181.21	1.22	5.72	29.15	44.1	2.25
3	100 year	166.72	1179.18	1180.68	1.5	3.94	42.35	53.02	1.41
4	100 year	166.72	1176.11	1177.15	1.04	6.69	24.93	43.9	2.83
5	100 year	166.72	1172.62	1174.63	2.01	5.72	29.16	26.59	1.74
6	100 year	166.72	1172.82	1175.3	2.48	2.52	66.21	41.63	0.64
7	100 year	166.72	1173.18	1174.66	1.48	3.31	50.46	46.01	1

Notes:

Q-total: total discharge, Min Ch El: min channel elevation (is elevation of each station, W.S Elev: Elevation of water surface, Water Elev: water elevation, Flow Area: Area that flood covers, Top Width: Maximum of elevation of flood surface, Froude Chl: Froude number that can be critical, sub-critical of hyper-critical.

Figure 6. (A) Flooding zones in 3D schema (B) water level in a cross section.

Figure 7. Inundation zones limits in a Google Earth background. Source: Author.