Guest Column: The Marriage of Surveying and Civil Engineering
As flood insurance premiums keep rising and floodplain technical requirements keep expanding, the involvement of surveyors and engineers is growing exponentially and their marriage, in this area in particular, is becoming more and more important. This article takes a look at the history of floodplain programs, their current role in preventing recurrent flood damages, and how surveyors and civil engineers work together to produce those results.
You can say that since the days of Noah, flooding has been a concern for mankind, albeit to a lesser extent than Noah faced, but through the years it still presented a formidable challenge and does to this day. It’s a challenge we have been learning to deal with.
As major floods occur in the U.S., our first efforts are directed to clean-up operations, then later we began to concentrate more on construction of structures to prevent flood waters from reaching damageable properties.
Major floods in the 1900s became the driving force for the Flood Control Act (FCA) of 1936, which created a federal program to provide flood protection. It authorized “civil engineering projects such as dams, levees, dikes and other flood control measures through the United States Army Corps of Engineers and other Federal Agencies.” The Corps was an easy choice as it had been established June 16, 1775 as a civilian force (George Washington appointed Colonel Richard Gridley as its first chief of engineers) to provide engineering, design and construction expertise to support the military in times of war. Later, under the Commerce Clause of the U.S. Constitution, the Corps was assigned responsibility for navigation on the nation’s waterways.
The 1936 Act, signed on June 22, 1936 by President Franklin Roosevelt, established an enormous commitment by the federal government to protect the people and property on approximately 100 million acres of land. The projects had to have a positive benefit-to-cost (B/C) ratio, and local governments had to provide the lands, easements and rights of way; agree to hold and save the Federal Government free from damages and to agree to operate and maintain the completed works.
The following year, a huge flood, which became known as the Super Flood, occurred on the lower Ohio River. In many cities along the river the flood waters reached into the second story of downtown businesses and stretched across the residential areas. In my hometown, Ironton, Ohio, (1937 population about 15,000) to commemorate the 50th anniversary of the flood, the local newspaper reported that 90 percent of Ironton was under water and 10,000 people were homeless and that a Corps of Engineers Report noted that Ironton was inundated to an average depth of 11 feet with depths of 12 to 15 feet recorded in the main business district. This flood is well remembered by senior citizens, and in many cities and towns the High Water Marks are still provided on street signs. This flood resulted in the 1937 FCA, which authorized $25 million for initial construction of flood control works along the Ohio and Mississippi Rivers.
Following that flood, in 1938, the Corps immediately began to design and construct floodwalls along the rivers. At that time, without a solid history of hydrological events upon which to base designs, most of the flood walls were designed to be 3 feet above the Flood of Record. Today, the existence of a system of flood control dams and reservoirs on major tributaries has significantly reduced the threat of flooding along both the tributaries and the rivers’ main stems.
Focus on Prevention
In addition to protecting existing property, some flood-free lands were now available for development inside the flood protection works. Also, as flood-prone lands outside the protective works continued to be developed, flood damages were still occurring, and it became more and more apparent that a different approach was needed to prevent the continual increase of flood damages nationwide.
To initiate the effort and to provide background data, the Corps was tasked to provide technical reports for a few representative areas providing information on historical flood damages, areas inundated, degree and frequency of flooding, storm related weather conditions, type, extent of damages, etc. Following the analysis of these reports, and the motivation provided by Hurricane Betsy’s flood surge in Florida and Louisiana in 1965, the 1968 Flood Insurance Act was enacted and became a “game-changer” which re-focused the attention from protection to prevention.
The 1968 Act was amended by the Flood Disaster Protection Act of 1973, which made insurance mandatory for the protection of property within SFHA’s (Special Flood Hazard Areas, aka Floodplains). The program has also been amended several other times, mostly with respect to insurance premiums.
The National Flood Insurance Program (NFIP) was established with the Federal Emergency Management Agency (FEMA) to manage the federal program. Its goals are “To provide for flood insurance for structures and contents in communities that adopt and enforce — minimal floodplain management standards,” and “To identify areas of high and low flood hazard and establish flood insurance rates for structures inside each flood hazard zone.” The law is administered by FEMA, which is now part of the Homeland Security Department. The primary role has been delegated to the states and the day-to-day operations have been further delegated to the city and county floodplain administrators.
Under this law, FEMA has developed a nationwide system of maps that display the flood-prone areas by zones of risk and degree of technical accuracy. FEMA has, thus, defined the floodplain boundaries and relevant flood elevations for the entire United States and mandated the degree of acceptable flooding. Their maps are known as Flood Insurance Rate Maps (FIRM’s). FIRM’s are used for establishing Flood Insurance premiums. Flood insurance must be purchased for all development being built in a designated SFHA. Also in accordance with these Acts, FEMA has mandated very specific requirements and the elevations shown on FIRM’s must be recognized in any proposed development in a designated SFHA. No project can adversely affect upstream neighbors or reduce the flood–carrying capacity of a stream. County ordinances specify the requirements for permits and development in an SFHA or Floodway. Floodplain permits are issued only for projects that comply with these regulations.
Permit applications must provide relevant survey data along with details of a proposed project, and a hydrology and hydraulics (H&H) study must document the calculations and supporting project conclusions about flooding impacts created by the proposed floodplain developments. Each county has published a Flood Insurance Study (FIS), which provides substantial basic data required for many H&H studies for these local streams and floodplain related studies. FISs also provide data for five flood frequencies, namely the 2 percent, 1 percent and 0.5 percent annual occurrence frequency.
The major role for surveyors and engineers falls under the 1973 law using these FIRM, FIS and county ordinances. The areas and limits of flood zones are determined by surveys and H&H studies. In order to provide a standard without regional discrimination, the 1 percent annual-chance-flood was adopted by FEMA as the base for floodplain management purposes, and these contours depict regulatory limits known as the Base Flood Elevation (BFE). The 2 percent chance is used to indicate additional areas of flood risk to communities. It should be noted here that for years the 1 percent and 2 percent chance was misnamed the 100-year and 50-year flood, respectively. This created a false impression that should these floods occur, they wouldn’t occur again for 50 or 100 years, promoting an expectation that leads to disregarding the actual dangerous occurrence frequency.
The percentages are based on statistical analysis of historic floods to indicate the calculated risk of an annual occurrence. Floods can and do occur in any year and/or in successive years.
Floodways are developed as tools to assist local communities in carefully managing their floodplains. They have been established along major streams as areas which have the capacity to carry the 1-percent-chance flood. A Floodway is also calculated to provide a capacity to convey the additional component of floodwater that would be generated by development of land in the floodway fringe adjacent to the floodway, thereby permitting expected development in this fringe to occur without adversely affecting the established BFE. No encroachment on the designated floodway is permissible unless it can somehow be mitigated. Engineering H&H studies and reports are always required by the county floodplain ordinances to assure the floodway’s flood-carrying capacity is not adversely affected. See the “Decision Flow Chart,” which determines floodplain permit and study requirements.
Creation of FIRM’s is not an easy task. The vagaries of flooding characterizes the various types of flooding, which must be addressed. In the East, floods generally result from heavy rains, sometimes on snow, and some drainage areas are very large — for example, for the Ohio River (which runs 981 river miles from, Pittsburgh, Penn., to Cairo, Ill., through six states). Its drainage area extends from the crest of the Appalachian Mountains to its confluence with the Mississippi River at Cairo and, at Huntington, W.V. (311.1 River Miles below Pittsburgh), the drainage area is nearly 36 million acres. In the West this same scenario may be present, but also sometimes — particularly in desert areas like the Las Vegas or Southern California areas — thunderstorms occur only in the mountains but release a torrent of flows down upon the low lands carrying not only water but also huge boulders and mud onto developed areas, creating horrendous damages.
Further, the directions of these flows is difficult if not impossible to predict as the boulders and mud sometimes cause the path of flow to be diverted, leading the flood flows to another nearby area. Another hazard arises from wildfires, which denude the land causing runoff to increase and mud slides to develop. These events are common in the West, but not so much in the East.
FIRM maps are developed through contracts with engineering consulting firms. The NFIP has mandated very specific requirements related to the Federal Flood Insurance Act. This leads to requiring the governmental, financial and insurance entities to have documentation of the specific elevations being proposed (and later to be built) on a FEMA “Flood Elevation Certificate” signed by a licensed professional surveyor or engineer. While an engineer can and usually would establish the proposed Finished Floor Elevation of a project feature, a surveyor must provide the elevations of the surrounding land in the floodplain as specified on the form, e.g. the lowest and the highest adjacent grades (LAG & HAG). These surveys must be accurate to the nearest 10th of a foot.
A county floodplain permit, along with an H&H Analysis, is required for all development in any identified flood zone or floodway. Encroachment on the floodplains, such as structures and fill, reduces the flood-carrying capacity, increases flood heights and velocities, and increases flood hazards in areas beyond the encroachment itself.
FEMA, recognizing that many flood zone determinations rely on aerial photography and computer programs that map in proximity, has provided a method for making corrections through a Letter of Map Amendment (LOMA) or a Letter of Map Revision (LOMR). Note that the photography should be up to date. A LOMA is to advise FEMA that the elevation of a certain location (structures or legally recorded parcels or portions thereof) is not in the Zone shown on the FIRM and to request its removal from the Special Flood Hazard Area. LOMA applications include the FEMA form, along with an Elevation Certificate, copy of the deed, Firmest, plat map, etc. The requested change must be certified by a registered professional engineer or licensed land surveyor. In our area, it is not unusual for a single tract of land to have a high area (where the home will be located), then slope down to a stream where a flood zone exists. The normal flood hazard review of the property for a financial transaction will discover the floodplain and document the need for flood insurance for the tract. Our surveyors are routinely able to apply for an eLOMA to remove only the structure from the floodplain and negate the need for flood insurance.
A LOMR is FEMA’s modification to an effective FIRM. These modifications are generally based on implementation of physical changes that affect the hydrologic or hydraulic characteristics of the flood source and thus result in a requirement to change the existing regulatory flood BFE or the SFHA. A LOMR based on filling is called LOMR-F. A LOMA or LOMR based on a proposed plan is called, respectively, a Conditional Letter of Map Amendment (CLOMA) or a Conditional Letter of Map Revision (CLOMR). A LOMR Application must have an accompanying H&H study by a professional engineer along with other data. It officially revises the FIRM. All requests for a LOMR must be made in writing by the CEO of the community or an official designated by the CEO. The approved LOMR is a public record.
Complete guidance and directions are available on the FEMA websites.
The marriage of surveyors and engineers is of paramount importance in obtaining quality end products from the many combined factors that meld the host of components, which must be derived and coordinated. Its very nature requires close coordination, mutual respect and trust between these professionals from A to Z in project endeavors. Without it, poorer quality along with schedule and cost overruns results. With it comes success and happiness. As partners, we must always remember that no flood plain/floodway analysis is correct if the surveys have a flaw.
In our firm, it has taken a period of time to fully jell, but our surveyors, engineers and AutoCAD staff have worked together to successfully assure that field collection, recording and mapping meets the needs (including the level of detail) of the engineering work to be undertaken. We can all agree that there is no need to collect unnecessary information, but there is a definite need to assure all needed information is gathered the first time out. It is a well-accepted fact here that no engineering analysis can be done well if we have incomplete, inadequate or faulty survey data.