FEMA’s Flood Insurance Rate Maps (FIRMs) or just Flood Maps are provided after a flood risk assessment has been completed or updated for a community.  This study is known as a Flood Insurance Study.  The FIRM gives you the Base Flood Elevations (BFEs) and insurance risk zones in addition to floodplain boundaries.  The FIRM may also show a delineation of the regulatory floodway.

Once the “insurance risk zone”  (commonly referred to as the flood zone) is determined, actuarial rates, based on these risk zones, are then applied for newly constructed, substantially approved, and substantially damaged buildings.  FEMA uses these rates to determine the insurance rate you will pay for flood insurance

FEMA’s Digital Flood Maps

FEMA discontinued the production and distribution of paper flood maps in 2009 as part of its Digital Vision Initiative. This affected all the Flood Maps, boundary information, and study reports. However, clients can still view the products for free through their website or buy them in digital format.

To view these flood maps online, go to FEMA’s Map Service Center and key in your address (hi-lited area shown here) search for your home.  This will prompt you to then select the map that covers your area.  The Flood Maps are somewhat cumbersome to use online. It is best to go through the tutorial on the bottom right of the address search page for an easier and more effective use of the GIS map.

No injury was reported on the said event. The said damn was built in 1935, as were a number of them during the Work Programs after the Great Depression. In 2007, it was inspected by a Department of Game, Fish and Parks Engineer and he noted that they “were satisfied with the condition of the dam” during that time. It was then again inspected in 2008 and it was said that the dam breach “was caused by an extraordinary natural event and not by any structural weakness in the dam.” (Photograph by Laura Wehde/The Daily Republic).

Earth dams are almost too numerous to count around the country. In fact, you might just be living near one without you knowing it. A great percentage of these dams were built over 70 years ago and, in many cases, the owners today were not the same ones when they were initially built. For this reason, maintenance and inspection of these dams became less popular.

FEMA estimates “there are over 80,000 dams in the United States”, and that approximately “one third of these pose a ‘high’ or ‘significant’ hazard to life and property if failure occurs.”

The South Fork dam, the country’s worst dam failure disaster in May of 1889, took over 2200 lives and almost half of which were under 20 years old. This incident happened in the town of Johnstown, PA, thus it was known as the “Johnstown Flood”. A 37-foot high wall of water hit Johnstown, located 9 miles downstream from the dam. It almost destroyed the entire city as 1600 homes and 280 businesses was flushed away.

In March 1928, the St. Francis Dam in California also failed. This caused a legislation to be enacted in and around the said state. This, and other later legislation led to life-saving advance warning when the Baldwin Hills dam near Los Angeles, California failed on December 14, 1963. Because of the advance warning which enabled the evacuation of approximately 16,500, the casualties from dam failures has significantly decreased to 5 individuals

Even though there have been far less loss of lives in the United States from dam failures since the 1970’s, reports that…

there were 132 dam failures and 434 “incidents” between January 2005 and January 2009.

Of course, It should be noted that the failure of the earthen levees near New Orleans, LA during and after Hurricane Katrina are purported to be responsible for killing more than 1000 people.

Failure in The KaLoko Dam on the Island of Kauai, Hawaii in March 2006 has resulted to the death of 7 people. Two years after the said incident, developer James Pfluegar was indicated for manslaughter and reckless endangerment in relation to the dam failure. The incident had caused the country of Kauai and the State of Hawaii to pay out over $9 Million in of lawsuits after the failure.

Cause of Dam Failures

Heavy rains cause overtopping, which is by far the most common cause of dam failures. Dam spillways and structures are typically not designed for more than a 1-percent chance (aka 100-year) storm event. When a rain event exceeds this, the water starts to travel outside of the control spillway. This causes erosion of the soil on the dam from the excessive amount of water traveling over it. It is also possible for overtopping to occur from smaller rain events because of debris blockage of the outlet structure or spillways or because of settlement of the dam crest.

Foundation defects, including settlement and slope instability, cause about 30% of all dam failures.

Seepage or Piping causes the remaining 20% of the U.S. dam failures. Piping is the internal erosion caused by seepage under and through the dam. This usually happens around structures such as pipes through the dam and spillways. Seepage can also be caused by animals, like beavers, muskrats, groundhogs, and other rodents, burrowing in the dam, by roots of trees growing on the dam, and through cracks in the dam.  All earth dams have seepage resulting from water permeating slowly through the dam and its foundation. But this seepage must be controlled or it will progressively erode soil from the embankment or its foundation, resulting in rapid failure of the dam.>

What Should You Do To Protect Home?

Since the failure of a dam causes flood, your best option is to avoid building in a flood zone, unless you elevate and reinforce your home. Have your area surveyed and investigated for dam failure and flood determination so you’ll know if your dream house is safe to be constructed in that certain area.

Do you live downstream from a dam? Is the dam a high-hazard or significant-hazard potential dam? To find out, contact your state or county emergency management agency and/or visit the National Inventory of Dams. There are around 2,228 dams on the National Inventory in Tennessee. And among those, 636 are listed as high or significant hazard potential dams.

If you live downstream from one of these dams, find out who owns and regulates the dam. This information should also be available from the National Inventory of Dams.>

Next, find out if there is an Emergency Action Plan in place. Again, consult your state or county emergency management agency. (Tennessee Emergency Management Agency)

Strangely enough, Tennessee is the only state in the United States that has not passed dam safety legislation.

Copyright (c) 123RF Stock Photos

Most of you have probably never thought about land surveying until you needed it at some point. Many of us hear about land surveying all the time but never really give it much thought. Since an investment in land and/or a home will likely be the largest investment you will ever make in your lifetime, knowing where your property lines are becomes very important indeed.

The art of land surveying was developed centuries ago. In fact, it’s one of the oldest professions in the world. The fact that it was used by man at such an early time and is still being used now shows how important surveying is to our survival.

The different uses of Land Surveying

Surveying land has many uses. Boundary surveying, for instance, allows you to know where your property corners or property lines are. This is especially helpful when disputes with a neighbour or with other people arise in terms of where your property ends.

If your family wants to divide a tract of land and transfer ownership to other family members, a boundary survey is the first step to do so. If you’re having a building constructed, it is very important that you have the land surveyed to make sure that you are not encroaching onto other peoples’ property. A mistaken building location is very expensive to fix so you might as well invest in a boundary survey to prevent this.

A topographic survey, or topo survey for short, is another important type of land surveying. A topo survey is done to locate natural and man-made features on a particular parcel of land. A topographic survey is different in that the elevation of the land is surveyed which means it can show man-made underground features, retaining walls, utility lines and etc.

Before you start any kind of construction activity, it’s important to have a topo survey done in the area so they’ll have an accurate record of the land’s existing conditions. Yes, that spot with the new mall in the neighbourhood had to have a topo survey done first.

Now, a flood survey or flood determination – this is very important too. It isn’t evident just looking at a property whether you are at risk of flooding or not. And, in some cases, even looking at the flood maps doesn’t give you an accurate answer. The flood survey determines the elevation of the home and compares that to the base flood elevation.

This is the only way to be sure you’re not in a flood hazard zone. If you’ve just been told that you live in a flood-prone area, having that confirmed by a professional land surveyor would let you know how to best proceed.
When getting flood insurance, insurance companies would require an elevation certificate from you. A land surveyor would be able to assist you with this.

If a company wants to invest in another state, or if there is a national lender on a commercial project, they will likely need an ALTA Land Title Survey done before anything is constructed. An ALTA Land Title Survey is a lot like a regular boundary survey except that nationally accepted ALTA Standards are used to guide the surveying effort.

Land surveying standards vary widely from state to state and an ALTA Land Title Survey is used to cut down on this variation. Also, an ALTA Land Title Survey typically is more involved than the state standards variety. Because of this, an ALTA survey can be more anywhere from 50% to 200% more expensive than using the state standards only. If you need this type of survey, I suggest seeking an experienced land surveying company who is familiar with these additional requirements.

In summary, there are many uses for a land survey and for seeking the services of a land surveyor. If you’re unsure of your situation, consult Knoxville Land Surveying at (865) 249-0447 today or go to the Contact page and send us an email.