National Flood Policy—ASFPM 2015 Recommendations
B. Hydrology & Hydraulics
B.1. (a) Account for flood depths and velocities in
setting zones and insurance rates; new charts or
tools should be provided to insurance agents to
streamline rate selection, relates to A.19
B.1. (b) Provide flood depth grids as part of the
FEMA flood map series and encourage
communities to adopt those maps for
administering the NFIP requirements in their
community. Encourage CRS incentive credits for
this activity.
This is a tricky one Siavash. Break it up and keep it
simple. Insurance stuff should go in insurance
Question is if we want to say do separate map for
regs and diff process for ins
a. This sounds like a non-reg product to me.
Consider listing with the items from A1-5 above.
b. I’m not sure how this will be done. If I’m a local
community, I’m hesitant to adopt a whole suite of
maps.
b. If I understand the purpose of this item
correctly, this could be re-worded as “Flood depth
grids should be considered a regulatory product
and used as such by both insurers and those
implementing floodplain development standards.”
b. Comment and verification required. Maximum
Flood Depth this value might not coincide with
peak flow conditions especially in urban
environment or developed floodplain areas.
This is pretty much standard procedure now. I
would doubt there are any regression equations
out there that are done “by hand”
UNCLEAR WHAT DATA AND WHICH REGRESSIONS
YOU'RE REFERRING TO
B.4. (a) Incorporate future-conditions hydrology
and cumulative impacts into flood risk
determinations under the NFIP Flood insurance
studies should identify assumptions for hydrologic
estimates, especially for future conditions; adjust
planning and regulation to avoid transferring the
responsibility from those that cause the problem
to those that suffer the consequences.
b. Give good examples of “associated mitigation
actions”
This needs to include specifics such as:
1) purchasing flowage easements
2) buying flood insurance for affected properties
3) purchasing and relocating affected buildings
B.4.(b) Ensure that the cumulative impacts of
encroachments be incorporated into all flood risk
determinations such that there is no resulting
increase in flood elevations without associated
mitigation actions, such as purchasing flowage
easements, buying flood insurance for affected
properties and/or purchasing and relocating
affected buildings.
B.5. Fund and issue updates of National Weather
Service regional rainfall frequency curves
NFPPR Combined comm rec and comments
LL—isn’t this being done?
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National Flood Policy—ASFPM 2015 Recommendations
B.6. (a) Develop engineering models that are
properly calibrated to historic flood events to
reduce the uncertainty associated with the model
results before such models can be deemed
validated.
B.6. (b) FEMA needs to establish guidelines and
quality assurance protocols for evaluating all
models, including the unsteady and twodimensional models, reporting requirements
appropriate for these modeling techniques, and
for the development and review of floodway
boundaries derived from such models.
B.7. Promote engineering models that are open
source, public, user-friendly, and widely accepted.
This goal should not prevent the use of legacy
software where appropriate. Also, model
performance should not be sacrificed for userfriendliness.
Calibration does not = validation-talk to Lulloff
This is connected to B5 without measurements
there is no calibration and verification.
a. The USGS Flood Inundation Mapper uses flood
inundation libraries to produce real time flood
inundation predictions.
b. There is wealth of information and application
around the world. The issues here is not in model
but in modeler. Per review and proper
independent quality control must be
implemented. This is not only for 2D models.
Question received: what do we do with all the
existing closed source models/mapping already
accepted by FEMA?
Related to the other recommendations on
unsteady and 2-D models, most of the more
robust and comprehensive models (software) is
proprietary which does create a problem with this
recommendation. Need to move to open source
Honeycutt: Models, or just model input/output? I
see issues with calling for all the models
themselves to be open source and public. There is
a public interest in knowing the scientific and
computational underpinnings of any model used
as the basis of floodplain mapping under the NFIP
(at a minimum), and we should retain and
strengthen as needed any protections that ensure
that even proprietary models are evaluated by
FEMA, USACE or others before acceptance.
Beyond that, I don’t think ASFPM should appear to
be saying that there can never be a proprietary
model used in the program – that would certainly
stifle innovation.
Is this really achievable? Rest of the world is more
focus on applicability, service, quality, continuity of
operation, knowledge transfer and overall cost of
applications for project. In comparison most of the
mapping is done by ESRI tools. (which are private
and definitely not open source) Open source tools
also require specialized knowledge, training and
skills.
NFPPR Combined comm rec and comments
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National Flood Policy—ASFPM 2015 Recommendations
B.8. Calculations of flood flow frequencies should
be determined based upon a 95% confidence level
(if feasible??) to reduce the uncertainty in
associated flows used for flood risk
determinations. Model convergence and
sensitivity analysis are prerequisites to the
estimation of meaningful confidence levels.
I think you want to be careful here. We seem to
be choosing the most conservative estimates for H
& H at each step, are we stacking probabilities to
the point where we won’t have believable
products? Just a thought.
This has been covered sufficiently in statements
above.
Also phrased “B.9 Use the 1% chance flood plus
future conditions and freeboard for mapping and
regulation, while incorporating and accounting for
the natural ecology of a system to avoid overengineered approaches to flood mitigation. “
B.10 Future conditions hydrology should look at
both future floodplain loss of storage? and future
changes in hydrology
NFPPR Combined comm rec and comments
LB—consider using 0.2% in urban areas
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