ICHARM Commemorative Symposium
Tokyo, Japan 14 – September - 2006

Flood Management in South America
Dr. Carlos E. M. Tucci
Institute of Hydraulic ResearchFederal University of Rio Grande do Sul

Urbanization
High rate of urbanization increase in developing countries,
mainly in Latin America where most of the countries areabove 75% of Urban population.
High Population increase rate in the city limits;
Increase on the impervious areas and flow canalizations inside
cities limits
Unregulated occupation by low income population in risk
areas such: hill slopes and flood plains;
In January of 2004 in Brazil died 84 persons due to flood
events.

Types of floods
 Flood plain are the natural
floods in which the impacts aremainly due to the lack of thecontrol of occupation of risk
areas;
 urban drainage floods aremainly due to the increase of
the peak and overland flow
after the increase of theimpermeable areas and flow
velocity on the sewers.

Leito maior de inundação
Leito menor

QUrbanRuralTimeFlood Plains impacts
 population moves to flood
plains after some years of low
floods.
 When comes a high level
flood the damage cost are highand created an economicalproblem; hill slope occupation
 flood plain risk areas
occupation
 mainly by low income
population

NormalFlow
União daVitória

1983 Flood

Main Causes
 lack of land use regulation andenforcement;

lack of prevention measures; indirect incentives: cities
receives funds without repayment
after a flood and do not needbiding to spend it bad management

Santa Fé – Argentina
Floods inside the diques
due to upstream
entrance

Urban Drainage Floods
população20

inundações

2000

15
101000

500

1920

1940

1960

1980

2000

2020

2040

anos

Belo Horizonte – population andflood increase

eventos de inundação

253000População (1000)

 Mainly due the increase of
the impervious area anddecreasing of concentration
time by conduits andchannels.
 Latin Americanurbanization was very highafter 1970. For instance,
Brazil increases its urban
population from 55,9%(1970) to 82% (2000) in 30years

Population increase and its relationship toimpervious areas
807060Impervious area %Curve obtained
based on data from
Curitiba, São Pauloand Porto Alegre,
three major cities ofBrazil

50403020
100050100150urban density, inhab/ha200250

Total Solids and obstructions

PORTO ALEGRE

 Obstructions
 Garbage Lack of maintenance Bad design
BELO HORIZONTESÃO PAULOErosion and Total Solids
 Stage 1 : increasing thecity and high productionof sediments;
 Stage 2 : Transition fromsediments to garbage ; Stage 3: when the city isalready constructed
reducing the sedimentand increasing thegarbage.

Urban Erosion

Urban Drainage Flood Management
Flood transference Fist stage: some floods
areas Second stage: drainage
canalization transferring
floods to downstream; Third stage: floods again
in downstream reaches dueto the sequence of works; The society losses twice:high cost of the works andincreases the floods

Flood Plain Management
Before urban development

Future scenario
urbanizationAA’(a) Basin view before urban development(b) second stage: new urbanization
upstream

QA(c)local view of flood areas and nearby
urbanization in the first stage(d) second stage: occupation of flood
areas and flood due to upstream
developments

Figure 7.2 Stages of basin occupation and impacts

Flood Management Sustainable Solution
 Urban drainage: (a) New developments can notincrease the natural flow; (b) Flood Management ofthe urban drainage basin; (c) induce the infiltration
on source control measures and damping in themajor drainages; (d) Recovery of the natural flowpaths
 Flood Plains: non-structural measures such asurban zoning; protection of slopes; and floodwarning

Management solutions
 For new developments is important to implement parks
for space reserve since it is required 1 to 2% of basin
area for urban drainage damping the peak flow to thechannels capacity; In flood zoning there is a need to give economical value
for the flood plains through environmental
compensation for private owners;
 For public areas there is a need for implementation ofpublic facilities in order to avoid invasion

How to move to it ?
 Legislation to control theoutput from the cities:
Federal or State legislation
to enforce it in the Basinand a Fund to finance thecities implementations. It isinterface of the Basin
Water Plan and citymanagement.
 Implementation by thecities through Urban
Drainage and FloodManagement Master Plan

State and Federal
Management asinternal boundary
conditions

Metropolitan
AreaManagementIntegrated Urban Waters management
Urban MasterPlan

Stormwaters
SolidsSewers
Watersupply

Urban Waters facilities

Scenarios
Water Facility Developed countries

South America

Water supply

Covered some risk ofwater sources

Covered in most of thecountries and high risk forwater sources

SewersHigh control

Stormwater& Solids

5-15% of waste
treatedMainly sediments and Lack of any control
quality control

Flood plains Mainly non-structural
measures

Lack of any control

Curitiba•Flood Control was a Project inside ofPROSAM, program funded by the Word Bank;•Flood Control planned stages were:ÐEmergencial actionsÐIguaçu Flood Plain controlÐUrban Drainage Metropolitan Area

Urban development
master plan

Urban drainage
and stormwater
management

Integrated water
resource catchment
planStrategic Management• Iguaçu flood plain has animportant pressure for occupation•If the river had its conveyance
increase the population will moveto plain as illegal development andwith urbanization it could increase
the floods again in the future•The plan was to develop a parallel
channel to protect the flood plainfrom invasion and reserve spaceand park development;•Reserve space in parks at thetributaries

Flood Plain and park
•Areas used for sandextraction•Park with 21 km2 is indevelopment

Areas planed and developed

Urban Flood Management of Porto Alegre Non-structural measures for urban drainage:
since 2000 the new development can not increase
natural flow;
 Urban Drainage Plan for six basins;
 Review of the flood control dike system (increase
flow of internal basins)

FLOOD PLAIN MANAGEMENT•Porto Alegre Metropolitan Area
has about 3 millions inhabitants;•Jacui/Guaiba lagoon and River
Delta has a basin of about 85.000km2;•Dikes constructed in 1970
•35 years without major floods;
major floods before 1967.
•Red line shows the existing dike;•Green area has its rainfall
pumped to the river system

Porto Alegre strategic management
evaluation

Description

US $billions

Cost of existing stormwater
network

1,1

Cost of the existing stormwater
network + the control of thefloods

1,4

Cost as the stormwater would besustainable constructed0,50União da Vitória Flood x hydropower
conflict
1. Population blame dam after
83 flood;
2. The Power Company
describe it as 1000 year flood;
3. 1992 occur another major
flood and population was very
mad about and did notbelieve;

Hydropower
damtown

4. After negotiations, nonstructural measures andknowledge about the floods
the relationship between thecompany and population isnormal.

Brazilian National Program on FloodManagement
Proposal asked by theCity Ministry in Brazil
Proposal developed anddiscussed in the govern
in 2004;
First phase ofimplementation isstarting in May/05

Legal instrument based onthe Water Law;
Inter-ministerial will start
the regulation discussion andproposal;
Capacity building at govern
level and funding agencies
Technical manual anddocuments to support theUrban Water Plans and related
actions

Brazilian National Program concepts
 Legislation : from the water
law any change on quantity
or quality requires permit
 Regulation: Cities will need
the permit and therequirement will be thedevelopment of the Urban
Sanitary and Floodmanagement Plan Four classes of cities:
A - > 500 K (30 cities)
B - < 500 and > 100 K (192)
C - < 100 and > 20 K
D - < 20K
 Starting with class A andmoving to the others
 US $ 7,3 billions in 24 years –investing 0,2 GDP
Total cities > 5 000.

Activities underway Technical documents:
development ofmanuals; books andpublications forcapacity building; Capacity building:federal govern andmany course throughthe country

 Term of reference forthree cities anddevelopment of thePlan with Ministery
follow up;
 Still in discussion in
the govern the legal
aspects

Conclusions
 Urban development and the present flood management are the main
source of the problems;
 Costs of channel improvements are increasing the floods and its costis up to 1000% greater than storage control; institutions issues such as: legislation (land occupation), capacity
building and law enforcement are the more important actions in themanagement plan; Interdisciplinary and integrate view of the city environment is the main
tool for management; need to build a sound institutional framework to deal with the Basin
Water Management which usually are based on national and State
govern management and the Integrated Urban Management which has
been a municipality management.