The pictures show progress of urbanization at Westside of Omiya Station1).
In Saitama city, the runoff ratio has risen from 40% around 50’s to 60% in 2007.
In addition, climate change or urban heat island may have increased weather extremes.
Extreme rainfall events of 50mm/hr or over have increased in Saitama City.
In 10-year period from 1997 to 2006, the number was nine.
Out of this nine, four events were observed in 2005 & 2006 alone1).
Urbanization and extreme rainfalls have been raising the vulnerability to flood2).
1) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku01.pdf
2) http://www.city.saitama.jp/www/contents/1205126406056/files/keikaku03.pdf
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