Paving the Way for Climate-Resilient Infrastructure - UN CC:Learn

Chapter 6: Internalization of Climate Risks in the Context of Planning and Urban DevelopmentPART IIThe ProblemThe geographical location of Mexico City helps sheds light on its current water problems and its vulnerabilityto the impacts of climate change. The city was developed on the low part of a closed water basin inthe Valley of Mexico on top of five lakes, and it is prone to floods. Since colonial times, lakes were dried upas a solution to frequent floods. One of the five lakes remains but continues up until the 20th Century wasto subject to regular floods. In the 1950s, the federal government undertook a major infrastructure projectto solve the floods problems in Mexico City. The infrastructure system put in place combines hundreds ofkilometres of deep drains, pump stations, and water treatment plants.The infrastructure system came on line in the 1970s, and it was expected to be a permanent solution toflood problems. Part of the system is used to drain out sewage from Mexico City, reducing the capacityof the system to cope with the extreme precipitation. Deficient maintenance in the system during almosttwo decades further reduced the capacity of the system. An additional problem has been the subsidenceof the urban area that has reverted the slope in some of the major drains. The federal and local governmentshave invested millions of dollars solving some of the most critical and immediate problems in thestorm water system, but it is clear the city needs to find a long-term solution to this critical problem. It isworth noting that San Salvador also has flood problems and needs to find a long-term solution to avoidmajor economic and social consequences. Flood problems in the two cities are impacted by climate variability,and they could become aggravated by climate change.TechnicalPresentation 1What a Country ShouldThink About andThen Do to AddressClimate Change andInfrastructure RisksTechnicalPresentation 2Internalization ofClimate Risks in theContext of Planningand Urban DevelopmentTechnicalPresentation 3A Framework forRisk Assessmentand Risk-InformedDecision-Making forInfrastructureDevelopmentFigure 6.4: Pre-Columbian Mexico CityTechnicalPresentation 4Probabilistic RiskModeling: BasicPrinciples andApplicationsTechnicalPresentation 5Note: Aztecs adapted to the area as the city grew by building structures called chinapa that floated over the lake;(Right) Modern-day topography of Mexico CityAn Economic Frameworkfor Evaluating ClimateProofing Investmentson InfrastructureRecent studies document that urbanization has led to an increase in precipitation in Mexico City over thelast 100 years (see Figure 6.5). Particularly important is the significant increase in extreme daily precipitationduring the last decades. Other studies have shown the ‘heat island effect’ in Mexico City has led tomicroclimates within the urban area creating significant differences in the concentration of precipitation(see Figure 6.6). These research results are relevant to the design of infrastructure (storm water). Whilerainfall is concentrated in the east and south, the current drainage system design assumed an equal distributionof rain throughout the city.TechnicalPresentation 6Supporting ElSalvador to ReduceInfrastructure Riskswithin a Green, Low-Emission and Climate-Resilient Frameworkfor DevelopmentPaving the Way for Climate-Resilient Infrastructure: Conference Proceedings 73