Message from Jim

In 1980, less than a week into my new job as an engineering/land surveying/drafting technician for the City of Biddeford, the first knowledge absorbed in this position pertained to the lack of qualifications required to prepare or revise a municipal assessor's map. It was a rainy day and without task, my former employer instructed me to revise various assessor's maps. Thirty years later, that walk down to the assessing department is still part of my life. One thing I have learned throughout this experience: caution should always be used when utilizing assessor's maps.

Though assessor's maps have a special purpose, documenting approximate acreage for all parcels within its municipality for land taxation, many individuals inside and outside the doors of each municipality retain the belief that each lot depicted on an assessor's map is the result of a completed boundary survey. With the aid of Geographic Information Systems (GIS) and technology, this misconception continues to grow.

Unfortunately, it is not uncommon for municipalities, design consultants, developers, and the general public to rely heavily on assessor's maps and GIS overlays to determine building setbacks, building envelopes, land divisions, flood risk, design, permits, and land purchase decisions. The purpose of this article is to convey that merging various types of data into one product, as GIS does, actually creates more error rather than eliminate the error which existed individually in each component.

In no GIS definition will you find its stated purpose “to accurately determine boundary lines or setbacks of existing improvements from boundary lines”. Records research, field identification & location, and office computation are all mandatory steps in the process to accurately create or re-establish the location of a boundary line. Land divisions, building permits, and deed descriptions should only be created upon completion of formal survey work. GIS is a technology used for scientific investigation, resource management, and large scale planning, so all users of this very neat product should never overlook one of its primary weaknesses: it does not determine the location of boundary lines.

In a similar vein to boundary surveys, some flood determination companies, municipal code officers or floodplain administrators, architects, engineers, land surveyors, insurance agents, etc. are also analyzing initial flood risk with municipal GIS, Delorme Maps, Google Earth, or other mapping platforms. This is incorrect for the following two reasons.

As mentioned above, the first reason pertains to the product created by merging technologies with error into one, thus compounding error. A true respect and understanding of significant figures should not be overlooked. Enlarging or shrinking a plan or GIS platform to similar scale of another product is not a concept to utilize for the creation of values more accurate than the previous product. The computer, because of its default capabilities, will create more exact numerical values, but in mathematical theory, the value cannot be that exact. A simple math rule, “the least precise operand determines the precision of the result” should not be overlooked.

The second reason, and one of greater importance, is that flood risk analysis is required to be determined on the maps of the actual insurer, the National Flood Insurance Program (NFIP). This is a requirement for all communities participating in the program. Flood determinations based on horizontal scaling should only be used as a guide; elevations are needed to fine-tune flood risk. Often overlooked is the age of the original flood study and the many changes which have since occurred in each watershed.

The NFIP understands that the flood maps have their flaws, but requires that all risk assessments be performed on NFIP issued maps. Using alternate flood overlays could create financial consequences for the municipality.

The three components of the NFIP; insurance, regulation, and mapping all have specific roles. Many assume that insurance and regulations have identical regulation and requirements, but they do not. Regardless of your role within the program, diversify your knowledge and exceed client satisfaction. A deeper understanding of each component will aid in enhanced public service and safety.

~Jim

Learn more about flood insurance!

Visit the National Flood Insurance Program official website.

Learn about your flood risk and eligibility for a Preferred Risk Policy.

NOTE: there is a 30-day waiting period for new flood insurance policies. Don't get stuck in the flood!

Techniques
“Sustainable Communities” are learning that the decisions they make today inevitably shape their future development patterns. Those patterns, in turn, not only determine how much damage future floods will cause, but also how healthy the community’s riverine and coastal areas will be.

There are common-sense solutions to improve that decision-making process and build a more secure and livable future for any community. The No Adverse Impact (NAI) strategy, developed by the Association of State Floodplain Managers (ASFPM), is one of those common-sense approaches. The NAI principle is simple - the action of one property owner or community should not adversely impact the flood risks for other property owners or communities. Adverse impacts can be measured in terms of increased flood peaks, increased flood stages, higher flood velocities, increased erosion and sedimentation, or other negative impacts that the community considers important. Any flood impacts that are unavoidable must be mitigated to the fullest extent possible, and preferably within the same watershed. The true strength of No Adverse Impact is seen when proposed development actions that would affect local flooding, or the property rights of others, are permitted only when they are in alignment with the community’s locally adopted Plan that identifies the negative impacts the community wishes to avoid and / or mitigate.

No Adverse Impact techniques fit well within a sustainable development framework. Local governments can utilize these concepts by implementing comprehensive, watershed-based Plans that recognize existing hazards; using environmentally sensitive zoning ordinances; promoting floodplain management regulations that will protect the community from future flood losses; expanding floodplain, wetlands, and resource mapping; and adopting disaster-resistant Building Codes.

In Conclusion
In many communities, current approaches to land use and development are creating future disasters. The late Gilbert F. White said it best: “Floods are acts of nature, but flood losses are largely acts of man.” The NAI principles and a broad sustainability framework are key elements in avoiding future flood-related disasters and, also, promoting and preserving natural water-related resources at the local level. A community can “pay now” by implementing sustainability initiatives and utilizing No Adverse Impact floodplain management principles, or it will have to “pay later” in manpower, community resources, and cold hard cash post-disaster – the direction to take for a sustainable future for your community may seem relatively clear, but the looming question still remains: which direction will your community take?

For more information on No Adverse Impact (NAI) Floodplain Management click here.

Terri L. Turner, AICP, CFM, is the Development Administrator/Floodplain Manager/Hazard Mitigation Specialist for the Augusta Planning & Development Department in Augusta, Georgia, as well as the ASFPM No Adverse Impact (NAI) Committee Co-Chair and the Region 4 Director of the Association of State Floodplain Managers (ASFPM).