Evaluating dam safety in Brazil: a comparative analysis of international classification systems

Salgado, Sérgio Ricardo Toledo; Carvalho, Elsa; Viseu, Maria Teresa; Oliveira, Othon Fialho de

doi:10.1590/2318-0331.302520250024

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Scientific/Technical Article • RBRH 30 • 2025 • https://doi.org/10.1590/2318-0331.302520250024 linkcopy

Evaluating dam safety in Brazil: a comparative analysis of international classification systems

Avaliação da segurança de barragens no Brasil: uma análise comparativa de sistemas de classificação internacionais

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Dams provide essential services to society, but the consequences for downstream communities and the environment can be devastating when safety measures fail. This investigation examines Brazil’s dam safety policies, focusing on classification systems and emergency preparedness. Data from 2022 reveals serious shortcomings: over 14,000 dams are unclassified by Risk Category (RC), and more than half lack a Potential Hazard Associated (PHA) rating. Of the 1,235 dams classified as high risk, only 106 have an Emergency Action Plan (EAP). The study compares Brazil’s system with international frameworks from institutions such as ICOLD, FEMA, USACE, and countries including Portugal, Spain, New Zealand, Australia, South Africa, Argentina, and Canada. While Brazil’s approach aligns with global standards, critical improvements are needed. The study proposes practical adjustments to enhance hazard classification and emergency planning. Future research could explore these proposals through case studies to better guide policy and protect lives.

Keywords:
Dam safety; Dam classification; Hazard classification; Emergency preparedness; Policy improvement

DAM	Year	Type of dam	Consequences
Euclides da Cunha	1977	Water Storage	Armando Salles Oliveira (Limoeiro) power plant and Coronel Soares hydroelectric plant experienced significant impacts, resulting in their incapacity to operate
Fernandinho	1986	Tailing Dam	7 fatalities
Mineração Rio Verde	2001	Mining Tailings	5 fatalities, along with disruptions to water supply, power, and roadways
Cataguases	2003	Industrial Waste	Disruption of water supply for some cities
Camará	2004	Water Storage	5 fatalities and 800 people left homeless
Rio Pomba Cataguases	2006	Industrial Waste	Disruption of water collection
Rio Pomba Cataguases	2007	Industrial Waste	765 people displaced
Algodões	2009	Water Storage	11 fatalities and 2 500 people left homeless
Fundão	2015	Mining Tailings	19 fatalities, population displacement, disruption of water supply, and environmental degradation along a 600 km stretch from the Doce River to its mouth
Herculano	2014	Mining Tailings	3 fatalities
Brumadinho	2019	Mining Tailings	270 fatalities

Dam Type	Classification	Reservoir Volume (hm³)
Water Storage Dam	Small	≤ 5 hm³
	Medium	> 5 hm³ and ≤ 75 hm³
	Large	> 75 hm³ and ≤ 200 hm³
	Very Large	> 200 hm³

Matrices	Descriptors	Score range
Technical Characteristics Matrix (TCM)	Height (a)	0 to 3
	Length (b)	2 to 3
	Type of construction material (c)	1 to 3
	Type of foundation (d)	1 to 5
	Age (e)	1 to 4
	Design flow conditions (f)	3 to 10
	TC = ∑ (a to f)	8 to 28
Conservation Status Matrix (CSM)	Reliability of spillway structures (g)	0 to 10
	Reliability of outlet structures (h)	0 to 6
	Seepage (i)	0 to 8
	Strains and Settlement (j)	0 to 8
	Slopes or faces deterioration (l)	0 to 7
	Navigation Lock (m)	0 to 4
	CS= ∑ (g to m)	0 to 43
Safety Plan Matrix (SPM)	Existence of project documentation (n)	0 to 10
	Organizational structure and technical qualification of dam's safety staff (o)	0 to 6
	Procedures and routines of dam safety inspections and monitoring (p)	0 to 8
	Operating rules for outlet hydraulic structures (q)	0 to 8
	Dam safety reports with analysis and interpretation (r)	0 to 7
	SP= ∑ (n to r):	0 to 39

Descriptors	Classification	Description	Score
Reservoir Volume	Small	< = 5hm³	1
	Medium	5 to 75hm³	2
	Large	75 to 200hm³	3
	Very Large	> 200hm³	5
Potential loss of human life	None	There are no permanent/resident or temporary people/transiting in the area downstream of the dam	0
	Infrequent	There are no people permanently occupying the area downstream of the dam, but there is a neighboring road for local use	4
	Frequent	There are no people permanently occupying the area downstream of the dam, but there is a municipal or state or federal highway or other place and/or enterprise where people may be affected	8
	Existing	There are people permanently occupying the area downstream of the dam, therefore, human lives could be affected	12
Environmental impact	Significant	The affected area of the dam does not represent an area of environmental interest, areas protected by specific legislation or is totally out of character for its natural conditions	3
Environmental impact	Very significant	Dam affected area has relevant environmental interest or is protected by specific legislation	5
Socio-economic impact	None	There are no navigation facilities and services in the area affected by the dam accident	0
	Low	There is a small concentration of residential and commercial, agricultural, industrial or infrastructure facilities in the affected area of the dam or port facilities or navigation services	4
	High	There is a large concentration of residential and commercial, agricultural, industrial, infrastructure and leisure and tourism services facilities in the affected area of the dam or port facilities or navigation services	8

Descriptors	Classification	Description	Score
Environmental impact	Little Significant	when the affected area of the dam does not represent an area of environmental interest, areas protected by specific legislation or is completely deprived of its natural conditions.	1
	Significant	when the affected area includes protected areas of sustainable or when it is an area of environmental interest and is little deprived of its natural conditions	2
	Very significant	when the affected area includes areas of strict protection, including Indigenous Lands – or when it is of great environmental interest in its natural state	5
Socio-economic impact	None	when there are no navigation facilities and services in the area affected by the dam accident	0
	Low	when there are 1 to 5 residential installations and commercial, agricultural, industrial facilities or infrastructure in the affected area of the dam	1
	Medium	when there are more than 5 to 30 residential and commercial, agricultural, industrial or infrastructure facilities in the affected area of the dam.	3
	High	when there is a large concentration of residential and commercial, agricultural, industrial, infrastructure and leisure and tourism services facilities in the affected area of the dam or port facilities or navigation services	8

RC	PHA
RC	High	Medium	low
High	A	B	C
Medium	A	C	D
low	A	D	D

RC	PHA
RC	High	Medium	low
High	A	B	B
Medium	B	C	C
low	B	C	C

RC	Purpose				Total
RC	Water storage	Hydroelectric	Mining tailings	Industrial waste	Total
High	2,254	315	52	14	2,635
Medium	2,345	95	96	-	2,536
low	691	893	307	11	1,902
Not classified	16,397	0	487	20	16,904
Total	21,687	1,303	942	45	23,977

PHA	Purpose				Total
PHA	Water storage	Hydroelectric	Mining tailings	Industrial waste	Total
High	2,926	588	254	21	3,789
Medium	893	94	164	-	1,151
low	4,202	621	403	5	5,231
Not classified	13,666	-	121	19	13,806
Total	21,687	1,303	942	45	23,977

Reservoir capacity	PHA
Reservoir capacity	High	Medium	Low	Not classified	Total
Very Large (> 200 hm³)	306	7	11	20	344
Large (> 75 hm³ and ≤ 200 hm³)	125	4	11	13	153
Medium (> 5 hm³ and ≤ 75 hm³)	613	73	80	82	848
Small (> 3 hm³ and ≤ 5 hm³)	202	32	69	116	419
Small (> 1 hm³ and ≤ 3 hm³)	521	100	287	485	1393
Small (≤ 1 hm³)	1,643	746	4,172	10,337	16,898
Without information	104	25	193	2,613	2,935
Total	3,514	987	4,823	13,666	22,990

Reservoir capacity	PHA
Reservoir capacity	High	Medium	Low	Not classified	Total
Very Large (> 50 hm³)	56	24	21	12	113
Large (> 25 hm³ and ≤ 50 hm³)	10	2	-	5	17
Medium (> 5 hm³ and ≤ 25 hm³)	55	16	1	2	74
Small (> 0.5 hm³ and ≤ 5 hm³)	54	33	17	16	120
Very Small (≤ 0.5 hm³)	100	87	346	85	618
Without information	-	2	23	20	45
Total	275	164	408	140	987

ICOLD	PNSB Regulation			Total	%
Classification	Regulated	Not Regulated	Undetermined	Total	%
Large Dams	2,013	29	15	2,057	8.6%
Small Dams	2,675	4,385	3,203	10,263	42.8%
Insufficient data	977	460	10,220	11,657	48.6%
Total	5,665	4,874	13,438	23,977	100%

Classification	PHA
Classification	High	Medium	Low	Not classified	Total
Large Dams	1,474	216	219	148	2,057
Small Dams	1,703	763	4,514	3,283	10,263
Insufficient data	612	172	498	10,375	11,657
Total	3,789	1,151	5,231	13,806	23,977

Criterion	Suggestion for Improvement	International Example
Dam Size	Assess whether incorporating dam size as a classification criterion would improve risk evaluation.	While dam size is relevant, classification should prioritize potential downstream damage to enhance safety.
Flood Assessment	Establish clear guidelines for “Sunny Day” and “Rainy Day” scenarios, differentiating between failures independent of natural floods and those occurring during floods.	Most international classification systems consider flood scenarios. ANEEL (Brazil) already applies similar criteria to hydroelectric dams; expansion to all dams could improve assessments.
Environmental Impact	Develop more detailed criteria for environmental impact assessment, moving beyond a binary approach.	Some classification systems, such as ANA’s, define protected areas, but a more advanced approach could quantify the affected area in the event of a dam breach, as used in Spain.
Socio-economic Impact	Enhance the socio-economic impact assessment by explicitly incorporating key infrastructure that, if affected, would significantly impact society.	Most international classification systems specify which types of infrastructure should be considered in this evaluation.
Population Affected	Introduce quantification of downstream residences for a more objective PHA assessment.	Portugal and Spain use the number of residences downstream as a classification criterion.

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[1] Adapted from Agência Nacional de Águas e Saneamento Básico (2016, 2020), Balbi (2008), International Commission on Large Dams (2001, 2011) and Mello et al. (2021).