What is a flood?

A flood is an inundation of land by the rise and overflow of a body of water. Floods occur most commonly when water from heavy rainfall, exceeds the carrying capacity of the river system, lake, or ocean into which it runs.  

What does the "100-year flood" mean?

The term "100-year flood" is misleading. It is not the flood that will occur once every 100 years. Rather, it is the flood elevation that has a 1- percent chance of being equaled or exceeded each year. Thus, the 100-year flood could occur more than once in a relatively short period of time. The 100-year flood, which is the standard used by most Federal and state agencies, is used by the National Flood Insurance Program (NFIP) as the standard for floodplain management and to determine the need for flood insurance. A structure located within a special flood hazard area shown on an NFIP map has a 26 percent chance of suffering flood damage during the term of a 30-year mortgage.  http://www.fema.gov/fhm/fq_rev03.shtm

What causes flooding in Houston/Harris County?

Houston area residents are subject to a tremendous amount of rainfall, which often occurs over an extremely short period of time.  This is generally due to unstable tropical storms.  Lots of rain, coupled with the extensive amounts of development that has made Houston a major metropolitan area, results in substantial flooding problem.

A lack of properly regulated development activity is a major cause of flooding and unfortunately this has been the case in Houston.

People in Houston need to understand how much rainfall we are likely to experience in the area.  In a 24 hour period, about 13 inches of rain will cause a 100 year flood, however with in Houston it is not unreasonable to see 2 to 3 times that much rain.  The tropical storms and resulting flooding from the 1994 storm and Allison were both in excess of 20 inches. 

When does flooding usually occur in Houston/Harris County?

Whenever it rains in sufficient quantities that existing runoff exceeds capacity of drainage systems.

Due to the increased number of storms with high rainfall, in recent years, unless the City of Houston and Harris County work to improve their flood management/preparedness capabilities, we can expect flooding to occur more often.

How can my property be in a floodplain? I have lived here for 20 years and I have not seen it flood yet.

Just because your property hasn’t flooded doesn’t mean it isn’t in a floodplain.  For example if your home hasn’t flooded in last 20 years, that means at a minimum in the past 20 years there hasn’t been a sig. Rainfall event that exceeded capacity of drainage system in your area/ as to make flooding a problem.  However, floodplains are getting larger/expanding as new development activities continue to occur in the area and rainfall intensities are seemingly getting higher.  This means that since you live in the floodplain, you should get flood insurance, and be prepared for a flood.  

I have lived here for years and never flooded. Why do I need flood insurance?

You need flood insurance to deal with the risk, especially now as it seems the risk will be greater.  The cost of flood insurance is worth it in terms of the money and aggravation you will save if you flood, but also the comfort having it gives you.

How can I determine if I am in a flood zone or floodplain?

Look at FIRM map. Maps are available from the City of Houston Planning office.  FEMA and the Harris County Flood Control District also have copies.  In addition you can find the maps online at www.e-floodmap.com.  This is courtesy of Dodson and Associates, a local engineering firm.

If I live in a floodplain, what are my chances of flooding?

Your chances of flooding are about 1% in any given year and close to a 30 percent chance of flooding over a 30-year mortgage

Are there any benefits to floodplain areas?

Floodplains act as nature’s detention ponds.  They are used to store floodwaters and convey them more slowly downstream.

Activities in floodplains that interfere with those purposes have a negative impact on lives and property.  Houses, buildings, and filling activities, are examples of activities that negatively impact the community since they cause flooding.  These are activities that in floodplain 1) remove areas in the floodplain that are used to store floodwaters or 2) block water from flowing.

However, soccer fields, golf courses, parks are excellent uses for the floodplain since they don’t take away storage areas, don’t block or interfere with flow of floodwaters, and serve as areas for public recreation except during a flood.

By knowing this one can hopefully understand the importance of preserving the floodplains so they can serve their intended purpose.

How do I get flood insurance?

Many homeowners insurance agents sell flood insurance through the National Flood Insurance Program.  The cost of a policy depends on the amount of coverage that will be purchased, and the location of the property.  Costs can range from $100 a year, to over $1000 a year.  The average cost nationally, is around $350.   It is important to get insurance as soon as possible, because there is a 30-day waiting period between the purchase date and the beginning of the coverage. For more information you can calling 1-888-CALL-FLOOD (1-888-225-5356) or looking online at www.fema.gov/nfip/.

Why has Harris County/FEMA created new flood maps?

Most of maps haven’t been updated for about 20 years, and everyone knows that flooding in Harris County has gotten worse over the last 20 years thereby indicating need for maps to be updated.

Happening now b/c of flooding experience during Tropical Storm Allison revealed/made obvious that flooding has increased over the past 20 years and maps were clearly wrong.  Even though many officials have known it for a while.  Allison revealed the big secret that the maps were a joke.

I understand that Harris County has created new flood maps. When will the new maps take effect?

The estimated time for the new maps to take effect is 6-12 months after they are released in draft form.  It is expected that FEMA and the Harris County Flood Control District will release the maps in the late summer of 2003, it is rumored to be in August.

Will I have to purchase flood insurance when the new map takes effect?

If property is in the newly mapped 100-year floodplain and you have a mortgage – your mortgage company will require flood insurance.