Geoscience Reference
In-Depth Information
5
Use of Radar Precipitation Estimates in Urban
Areas: A Case Study of Mexico City
Ernesto Caetano
1
, Baldemar Méndez-Antonio
2
and Víctor Magaña
1
1
Instituto de Geografía, National Autonomous University of Mexico,
2
Energy Department, Metropolitan Autonomous University,
Mexico
1. Introduction
Storm events have long been a menace to Mexico City. The main reason is related to the fact
that in summer, many showers can reach intensities of more than 20 mm/hour, which makes
difficult the management of the drainage system in various areas of the city. As instance
discharges of large magnitudes in the western part of the city are an element of danger, as they
lead to flash flood that inundate populated areas downstream in a matter of minutes. Recent
flooding events in Mexico City have revealed its vulnerability to severe weather conditions.
Although regularization programs and new urban land policies are been implemented by the
council government, there are still many families living in high risk areas. These areas over
hillsides, and irregular human settlements still proliferate. Usually, severe storms can cause
hazard landslides because unstable landfills and deforested hill slopes. On the other hand in the
flat parts of the city, faulty drainage systems usually cause sewage flooding after continuous
rain events. The urban sprawl undergone in the last half century, has not kept pace with urban
services such as drainage. In the rainy season, puddles arise, sometimes caused by the presence
of silt and debris in the ducts and the drainage system capacity is exceeded, and in other cases
there are no absorption wells in areas with problems in the drainage network. Additionally, the
lack of maintenance of dams and channels can also result in severe flooding problems. In most
cases, the intense rainfall events produce merely an emergency response of fire departments.
In the last three decades there have been major advances in remote sensing techniques for
estimation of rain, mainly in the use of meteorological radar and weather satellites,
increasing the availability of rainfall data for operational meteorological and hydrological
applications. Precipitation estimates derived from meteorological radar are useful in runoff
simulation in urban drainage. Spatial distribution of radar rainfall used as input to a
distributed hydrological model permit to characterize the performance of drainage
infrastructure at local and regional scale. Radar data used in this analysis are obtained from
C-band radar deployed at western Mexico Valley basin and derived rainfall estimates
provides the input to a distributed hydrologic model applied to the Mixcoac
microwatershed located at western Mexico basin. Radar and distributed hydrologic model
are capable to provide accurate rainfall and runoff data supporting specific-site flood
information and, also provides a baseline for comparison and guides design of radar
network as one component of an early warning system for the region.
