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Nashua River crossing

Allds St: Within Floodway at
Salmon Brook crossing

Pine Hill Rd: Within .2%
Floodplain near intersection with
Perimeter Rd

Manchester St: Within Floodway
at Harris Pond and within .2%
Floodplain near Tinker Rd

Broad Street Pkwy: Within .2%
Floodplain on approach to
Nashua River crossing and
crosses Floodway

Types of Roads Included:

Highways: The top of the
hierarchy. They are limited
access, provide largely
uninterrupted travel over long
distances and are designed for
high speeds. Example: Everett
Turnpike.

Arterial Roads: The next level of
roadways. They serve to move
large volumes of traffic through
a town or to connect one section
of town with another section.
Example: NH 101A

Collector Roads: Act to feed
traffic to or from local roads and
arterials. Collector roads provide
direct access to abutting
properties and distribute it to or

from arterials. Traffic using a
collector is usually going to or
coming from somewhere
nearby. Example: Henri Burke
Highway

rt

Entire jurisdiction.

NH DES Drought Management

Plan:

Level 1—Alert

Level 2—Warning
Level 3—Emergency
Level 4— Disaster

US Drought Monitor

DO—Abnormally Dry
D1—Moderate Drought
D2—Severe Drought
D3-Extreme Drought
b4— Exceptional
Drought

S—Short term, typically
less than 6 months
L—Long term, typically
more than 6 months

DO

D1

D2

D3

D4

short term dryness
slowing planting, grow!
of crops

some lingering water
deficits

crops not fully recovere

some damage to crops
streams, reservoirs, or
wells low, some water
shortages developing o
imminent

voluntary water-use
restrictions requested

crop losses likely
water shortages
common

water restrictions
imposed

major crop losses
widespread water
shortages or restrictior

Exceptional &
widespread crop loss
Shortages of water in

reservoirs, streams, &
wells creating water
emergencies

S
® impacts on agriculture
L
@ impacts on hydrology &
ecology
Overall:

Loss of crops.

Inadequate quantity of drinking
water.

Loss of water for fire protectior

Increased risk of fire.

uake

Entire jurisdiction.

Richter Scale:
@ <3,4 (detected only by
seismometers)
e >8 (total damage,
surface waves seen,
objects thrown in air)

For full definitions of Richter
Scale, see Section 3.5
Vulnerability by Hazard

Structural damage or collapse ¢
buildings.

Damage or loss of intrastructur
including roads, bridges,
railroads, power and phone
lines, City communications, Cit
radio system, power generatior
facility, domestic water, and
wastewater treatment plant.

Loss of water for fire protectior

Increased risk of fire from gas
break.

Risk to life, medical surge.

1e Temperatures

Entire jurisdiction.

Extreme heat—period of 3
consecutive days which air
temperature reaches 90F or
higher on each day.

Extreme cold— period of 3
consecutive days of minimum
temperatures at or below OF

Overburdened power systems
may experience failures due to
extreme heat.

Shortages of heating fuel in
extreme cold due to high
demand.

Medical surge.

Loss of municipal! water supply
for drinking water and fire
protection due to freezing
temperatures.

find Events

Entire jurisdiction.

Fujita Tornado Damage Scale:

® FO—winds <73 mph
F1—winds 73-112 mph
F2—winds 113-157 mph
F3—winds 158-206 mph
F4a—winds 207-260 mph
F5—winds 261-318 mph

Wind damage to structures anc
trees.

Damage or loss of infrastructur
including roads, bridges,
railroads, power and phone
lines, City communications, Cit
radio system, power generatiol
facility, domestic water, and
wastewater treatment plant.

Environmental hazards resultin
from damage.

Medical surge.

Loss of natural resources.

aus Diseases

Entire jurisdiction.

Disease epidemics.

Burden on healthcare facilities.

Large-scale incidents of food or
water contamination.

Extended periods without
adequate sanitation services.

Possible quarantine to prevent
disease from spreading.

de

Limited steep hills that are prone
to landslide in jurisdiction.

Sliding of a mass of soil, detritus,
or rock on or from a steep slope.

Structural damage or collapse ¢
buildings.

Damage or loss of infrastructur
including roads, bridges,
railroads, power and phone
lines, City communications, Cit
radio system, power generatio!
facility, domestic water, and
wastewater treatment plant.

Loss of water for fire protectior

Increased risk of fire from gas
break.

Risk to life, medical surge.

ng

Entire jurisdiction.

Areas with large populations
present outdoors and large open
spaces are particularly
vulnerable.

Lightning Activity Level:

e level 1
@ Level 2
e Level3
e Level 4
e Level5
e Level6

For full definitions of Lightning
Activity Level, see Section 3.5
Vulnerability by Hazard

Smoke and fire damage to
structures.

Disruption to power lines, traff
control systems, and
communications.

Damage to critical electronic
equipment.

Injury or death to people
involved in outdoor activity.

Winter Weather

Entire jurisdiction.

Depth of snow in a given time
frame (ex. 2 or more inches per
hour over a 12 hour period).

Blizzard—violent snowstorm
with minimum winds of 35 mph
and visibility less than % mile for
3 hours.

Ground snow load factor.

Ice Storm—Sperry-Piltz Ice
Accumulation Index:
@ O-—little impact
e 5-—catastrophic damage
to exposed utility
systems

For full definitions of Sperry-Plitz
Ice Accumulation Index, see
Section 3.5 Vulnerability by
Hazard

Disruption to road network.

Damage to trees and power
lines, communications, gas line

Structural damage to
roofs/collapse.

Increase in CO, other hazards.

torms and Space Weather

Entire jurisdiction

Solar flares—violent explosions
in the sun’s atmosphere.

Solar radiation storms—elevated
levels of radiation that occur
when the numbers of energetic
particles increase.

Geomagnetic storms—
explosions in the corona region
of the sun.

Space weather can produce
electromagnetic fields that
induce currents in wires,
disrupting power lines and
causing widespread power
outages.

Severe space weather can
produce solar energetic
particles, which can damage
satellites used for
communications, global

positioning, intelligence
gathering, and weather
forecasting.

al and Post-Tropical
es

Entire jurisdiction.

Saffir-Simpson Hurricane Wind
Scale:
e Category 1—sustained
winds 74-95 mph
e Category 2—sustained
winds 96-110 mph
® Category 3—sustained
winds 111-129 mph
® Category 4—sustained
winds 130-156 mph
e Category 5—sustained
winds 157 mph or higher

Wind damage to Structures anc
trees.

Water damage to structures an
their contents.

Damage or loss of infrastructur
including roads, bridges,
railroads, power and phone
lines, City communications, Cit
radio system, power generatio!
facility, domestic water, and
wastewater treatment plant.

Environmental hazards resultin
from damage.

Isolation of neighborhoods
resulting from flooding.

Water pressure, quality, and
capacity issues impacting fire

protection.

Loss of natural resources.

Forested areas in jurisdiction,
particularly in northwest and
southwest quadrants as weil as
in Mine Falls Park.

Areas outside of municipal water

NWCG Fire Size Classification:
e A-—greater than O but
less than or equal to
0.25 acres
e B—0.26 to 9.9 acres
e C—10.0 to 99.9 acres

Smoke and fire damage to
structures in wildland/urban
interface

Damage to habitat.

supply system. e D—100-299 acres Impacts to air quality.

@e E—300 to 999 acres

e F—1,000 to 4,999 acres Impact to roadways.

e G—5,000 to 9,999 acres

e H—10,000 to 49,999 Loss of natural resources.
acres

e I—50,000 to 99,999 Potential for urban
acres conflagration.

e J—100,000 to 499,999
acres

e K—500,000 to 999,999
acres

@ {—1,000,000+ acres

st step in determining the probability of future hazard events in the City on Nashua is to examine the location, extent, and impact of
us hazards. If a hazard event has not occurred within the City of Nashua but has occurred in the region it is also noted. These regior
are included as it would be reasonable to expect the event could have occured in Nashua. All SHELDUS data and recorded losses inc
lillsborough County.

azard event also includes a source for the data. The primary sources of data include the Nashua Hazard Mitigation Plan Update 201:
ampshire Hazard Mitigation Plan 2018 Update, neighboring Hazard Mitigation Plan Updates (Hollis & Hudson 2018 Updates) (unkno
| sources), Arizona State University Spatial Hazard Events and Losses Database for the United States (SHELDUS) 16.1 January 1960 t
iber 2016), & FEMA Presidential Disaster Declarations (1953-2018).

ble does not take hazard extent into account as a threshold for inclusion. As a result, many hazard events of a lower hazard extent n
documented. This will typically be found in more frequently occurring hazards such as inland flooding, lightning, and severe winter
or. Efforts should be made to improve municipal recordkeeping for smaller hazard events. A common example can be inland floodin:
that temporarily close roadways as a result of thunderstorms.

vazard events are included that occurred outside of the region but caused impacts to Nashua. Examples include tropical and post-trc
2s where the eye did not pass through Nashua but the wind and rain fields impacted the City and earthquakes where the epicenter |
een located far away but shaking was felt in the City.

‘or improvement in future plans is to compare authoritative data sources from NOAA, USGS, and other agencies with the SHELDUS a
Disaster Declaration loss databases to ensure hazard events that may not have had human, physicai, or financial losses are included
‘ables. This will provide a more comprehensive number of hazard events to calculate probability. Another recommendation is to

ent warnings, watches, and advisories from the National Weather Service issued for Hillsborough County. While these may not have
‘din an actual hazard event, these may provide more realistic estimates of conditions that could have been favorable for the hazard
ing leading to better probability estimates. Finally, it is recommended that this database be reorganized based on fundamental peril
rain, snow) to provide better estimates of the actual hazardous condition. Many hazards include multiple perils but are not clearly
ented across each category. An example is tropical and post-tropical cyclones which can also include inland flooding, lightning, high

Hazard

Hazard

Date Impact Crop Crop Crop Property | Property { Property | Sour
Location | Extent Damage Damage Damage Damage Damage Damage
within Adjusted | Per Adjusted j; Per
Jurisdicti Capita Capita
on

loading
October Merrima ; No No NH
z | 23,1785 | ck River historic historic 2018
data on data on
extent impact
April 21- | Merrima | Highest No NH t
z | 24,1852 | ck River flood historic 201
Stage in data on
70 years. | impact
Flood
waters 2
feet
lower

than
1785
flood.

uM

1927

Hillsboro
ugh
County

No
historic
data on
extent

Damage
to road
network.

Nast
HME
201:

we

March
11-21,
1936

Hillsboro
ugh
County

25-50
year
recurrenc
e interval

$133,000
,000 in
property
damage
and
77,000
homeless
througho
ut New
England.
Primary
impact to
structure
S,
infrastruc
ture, and
road
network.
Flooding
caused
by heavy
snowfall
totals,
heavy
rains,
and
warm

Nast
HME
201: