Miami: Climate Miami’s client is similar to Houston in several ways. It has one of the highest levels of rainfall of any major U.S. city. It receives an average of 58.6 inches of rain per year. Statistically it is the most likely major city to be hit by a hurricane in the world.
Miami: Geography The city of Miami is one of the most densely populated cities in the United States. The city itself encompasses 354.5 square miles an contains Miami Dade county encompasses 35.4 square miles and contains nearly 5.4 million residents. The city is located on the coast, making it vulnerable to hurricanes. To combat this there are several natural and man made barrier islands.
Miami: Geography The city’s drainage is heavily affected by the natural conditions around the city. Like Houston, Miami is located on a very flat piece of ground. The ground never rises above 40 feet above sea level and goes as low as sea level. The average elevation of the city is 6.2 ft above sea level. Because of its high water table, it is not possible to dig below 15 to 20 without hitting water. Because of this there is no subway system in Miami.
Miami: Local conditions Miami is much stricter than Houston in its development and building regulations. All development must take place above the Flood Criteria Elevations defined as the higher of the 10 year, 1 day ground water elevation or the 5 year 1 week ground elevation plus 18 inches. This elevation is determined by the septic tanks that are very common in Miami-Dade. The septic tank drains are commonly placed at 18 inches below grade, this prevents overflowing. The flood evaluation has not been re-evaluated in nearly 20 years.
Miami: Storm systems Miami Storm water Systems: Major Systems: These systems can handle storm waters over the 10 year limit approaching the 100 limit. These are usually main line underground piping and open water channels. Minor Systems: These systems are required to be able to handle up to and including a 10 year storm. These are a combination of below ground sewers and four lane roads for ten year storms, and two lane roads for five year.
Miami: Storm systems Positive Drainage: Direct drainage into open bodies of water. This is the least acceptable form of drainage since it is more likely to over flood. Onsite Retention: This is the most desired strategy. It can be implemented in several ways including: surface infiltration through grassy swales, underground seepage such as exfiltration trenches, and retention ponds. Dade county encourages 1 inch of retention.
Miami: Diagrams Shallow Grassed Swale Dry Detention Basin
Miami: Storm systems Commercial and industrial must provide at least ½” of dry detention or retention. Projects having greater than 40 percent impervious cover and discharge into receiving waters must provide at least ½” retention. All residential and commercial storm water management systems are required to withstand at least the 5 year flood.
Bibliography Information: Chin, David A. “An Overview of Urban Stormwater= Management Practices in MiamiDade County, Florida.” http://www.ci.miami.fl.us/cms/ Images: Miami-Dade Aviation Department: Storm Water System http://www.mapquest.com/444444 http://en.wikipedia.org/wiki/Miami