Classification of environmental fragility in watershed using Fuzzy logic and AHP method

Lira, Karen Carrilho da Silva; Francisco, Humberto Rodrigues; Feiden, Aldi

doi:10.14393/SN-v34-2022-62872

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Papers • Soc. nat. 34 • 2022 • https://doi.org/10.14393/SN-v34-2022-62872 copy

Classification of environmental fragility in watershed using Fuzzy logic and AHP method

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Assessment of environmental fragility in watersheds is an important tool to assist managers in planning and interventions for sustainable production and environmental conservation. The objective of this work was to use Fuzzy logic and the Analytic Hierarchy Process (AHP) method to classify environmental fragility using data obtained from public institutions. The Marreco River watershed in western Paraná, Brazil, was the study model. To classify areas, a geographic information system (GIS) and data from a digital elevation model (DEM), as well as data on soil occupation and type were used. The analysis found that 71.3% of the basin area has average fragility. Compared to two other forms of weighing elements of the slope map, the three presented statistical difference, but all indicated that the basin under study mostly has average environmental fragility. The use of fuzzy logic allowed application of a continuous variation of weights according to the variation of environmental characteristics, which may more effectively represent the reality and, therefore, provide more reliable results. This method may represent a useful tool to appropriately manage sustainable production and environmental conservation in watershed areas.

Keywords:
Multi-criteria analysis; QGIS software; Environmental vulnerability

Degree of fragility	Values
Very low	up to 2
Low	2 to 4
Average	4 to 6
High	6 to 8
Very high	8 to 10

Variables	Degrees of Environmental Fragility and Weights
	Very low	Low	Average	High	Very high
	2	4	6	8	10
Soil	Red and Red-Yellow Latosol, clayey texture	Yellow and Red-Yellow Latosol, medium/ clayey texture	Red Nitosol, Red Argisol, clayey texture	Red-Yellow Argisol, medium texture	Neosol, Cambisol, Gleysol
Land use	Forest formation	Pasture	Agriculture-pasture mosaic	Agriculture	Urban area

Degree of fragility	Soil			Land use and occupation
Degree of fragility		Area(km²)	%		Area(km²)	%
Very low	Red Latosol	93.5	27.6	Forest formation	63.9	18.9
Low	-	0.0	0.0	Pasture	8.1	2.4
Average	Red Nitosol	184.6	54.5	Agriculture-pasture mosaic	59.2	17.5
High	-	0.0	0.0	Agriculture	193.3	57.1
Very high	Neosol	60.7	17.9	Urban area	14.3	4.2
∑		338.8	100		338.8	100

Degree of fragility	Slope		Altitude
Degree of fragility	Area (km²)	(%)	Area (km²)	(%)
Very low	70.2	20.7	9.6	2.8
Low	170.6	50.4	86.9	25.7
Average	65.6	19.4	85.4	25.2
High	24.7	7.3	83.7	24.7
Very high	7.7	2.3	73.2	21.6
∑	338.8	100	338.8	100

	Comparison matrix				Normalized comparison matrix ^a				$(ω)$ ^b
	S	T	U	A	S	T	U	A
S	$1$	$4$	2	$7$	0.5283	0.4706	0.5581	0.5000	0.5142
T	$\frac{1}{4}$	$1$	$\frac{1}{3}$	$2$	0.1321	0.1176	0.0930	0.1429	0.1214
U	$\frac{1}{2}$	$3$	$1$	$4$	0.2642	0.3529	0.2791	0.2857	0.2955
A	$\frac{1}{7}$	$\frac{1}{2}$	$\frac{1}{4}$	$1$	0.0755	0.0588	0.0698	0.0714	0.0689
$\sum$	1.893	$8.5$	3.583	$14$					1
			$λ \max$ ^c	CI ^d	RI ^e	CR ^f
			$4.02285$	$0.0076$	0.90	$0.0085$

Degree of fragility	Area (km²)	(%)
Very low	0.5	0.2
Low	51.2	15.1
Average	241.6	71.3
High	44.7	13.2
Very high	0.8	0.2
∑	338.8	100

Degree of fragility	Method of assigning weight to slope map elements
	FZ	ModifiedFZ	ModifiedR
	Area (%)	Area (%)	Area (%)
Very low	0.2	0	0
Low	15.1	3.4	4.6
Average	71.3	57.2	63.1
High	13.2	37.7	31.1
Very high	0.2	1.7	1.3
∑	100	100	100
Mean calculated for degree of fragility *	${5.94}_{c}$	${6.80}_{a}$	${6.60}_{b}$

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E-mail: sociedade.natureza@ig.ufu.br

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[1] AUTHORS' CONTRIBUTION

Karen Carilho da Silva Lira carried out the creation, methodology, data curation, formal analysis of the project, projection, software, the original draft of the writing and the editing of the text. Humberto Rodrigues Francisco carried out the data creation, methodology, curation, formal analysis, visualization, software, supervision, and the review and editing of the writing. Aldi Feiden performed the writing, methodology, formal analysis, review and editing of the writing.

Less important	Extremely	$\frac{1}{9}$
		$\frac{1}{8}$
	Very strongly	$\frac{1}{7}$
		$\frac{1}{6}$
	Strongly	$\frac{1}{5}$
		$\frac{1}{4}$
	Moderately	$\frac{1}{3}$
		$\frac{1}{2}$
	Equally	$1$
More important	Moderately	$2$
		$3$
	Strongly	$4$
		$5$
	Very strongly	$6$
		$7$
	Extremely	$8$
		$9$

$n$	1	2	3	4	5	6	7	8	9	10
RI	0	0	0.58	0.90	1.12	1.24	1.32	1.41	1.45	1.49