Prepared in cooperation with the Federal Emergency Management Agency 

Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, 

and Alstead and on Warren Brook in Alstead, New Hampshire 

Open-File Report 2006−1221 

U.S. Department of the Interior 

U.S. Geological Survey 
Cover. Devastation along Warren Brook, Route 123 in Alstead, NH, after the October 8 and 9, 2005 flood. (Photograph courtesy of the 

New Hampshire State Police Aviation Unit) 
Flood of October 8 and 9, 2005, on 

Cold River in Walpole, Langdon, and 

Alstead and on Warren Brook in 

Alstead, New Hampshire 

By Scott A. Olson 

Prepared in cooperation with the 

Federal Emergency Management Agency 

Open-File Report 2006–1221 

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

P. Patrick Leahy, Acting Director 

U.S. Geological Survey, Reston, Virginia: 2006 

For product and ordering information:
 

World Wide Web: http://www.usgs.gov/pubprod
 

Telephone: 1-888-ASK-USGS
 

For more information on the USGS--the Federal source for science about the Earth, its natural and living resources, 
 

natural hazards, and the environment:
 

World Wide Web: http://www.usgs.gov
 

Telephone: 1-888-ASK-USGS
 

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 
 

U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual copyright owners to 
 

reproduce any copyrighted materials contained within this report.
 

Suggested citation:
 

Olson, S.A., 2006, Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren 
 

Brook in Alstead, New Hampshire: U.S. Geological Survey Open-File Report 2006–1221, 46 p., online only.
 
iii 

Contents 

Abstract...........................................................................................................................................................1
 

Introduction.....................................................................................................................................................1
 

Description of Investigated Reaches ................................................................................................1
 

Storm Characteristics ..........................................................................................................................1
 

High-Water Marks .........................................................................................................................................3
 

Peak-Discharge Estimates...........................................................................................................................3
 

Warren Brook at Mill Hollow ..............................................................................................................3
 

Warren Brook Downstream of Cooper Hill Road.............................................................................3
 

Cold River at Vilas Pool Dam...............................................................................................................6
 

Cold River Downstream of the Warren Brook Confluence ............................................................6
 

Cold River at the Drewsville USGS Stream-Gaging Station ..........................................................6
 

Flood-Flow-Frequency Characteristics......................................................................................................6
 

Summary........................................................................................................................................................10
 

Selected References...................................................................................................................................10
 

Appendixes 1–3.
 

1.	 Maps Showing Location of High-Water Marks Flagged in Walpole, Langdon, and 
 

Alstead, NH, Following the Flood of October 8 and 9, 2005 .................................................22
 

2.	 Profiles of the October 2005 Flood on Cold River and Warren Brook, 
 

Southwestern New Hampshire ................................................................................................30
 

3.	 Elevation Benchmarks Along Cold River and Warren Brook, New Hampshire ...............45
 

Figures 

1–2. Maps showing— 

1.	 Location of investigated reaches and the towns of Walpole, Langdon, and 
 

Alstead, NH...........................................................................................................................2
 

2.	 Locations where peak discharge and flood-flow frequency were estimated 
 

in Walpole, Langdon, and Alstead, NH ............................................................................4
 

3.	 Photograph showing view looking upstream at the Cooper Hill Road embankment 

failure October 2005 in Alstead, NH...........................................................................................5
 

4–5. Graphs showing—
 

4.	 Flood-flow frequency estimates for selected recurrence intervals at selected 
 

sites on Warren Brook, Alstead, NH.................................................................................7
 

5.	 Flood-flow frequency estimates for selected recurrence intervals at selected 
 

sites on Cold River, Alstead, Langdon, and Walpole, NH..............................................9
 
iv 

Tables 

1.	 High-water elevations and locations of the October 2005 flood on Cold River 

in Walpole, Langdon, and Alstead, NH....................................................................................14 

2.	 High-water elevations of the October 2005 flood on Warren Brook in Alstead, NH .......17
 

3.	 Basin characteristics and flood-flow frequency estimates for selected recurrence 

intervals at selected sites on Warren Brook, Alstead, NH....................................................6 

4.	 Flood-flow frequency estimates for selected recurrence intervals at selected 

sites on Cold River, southwestern New Hampshire, 2005......................................................8 

Conversion Factors, Abbreviations, and Vertical Datum 

Multiply By To obtain 

Length 

inch (in.) 25.40 millimeter (mm) 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

Area 

square foot (ft2) 0.09290 square meter (m2) 

square mile (mi2) 2.589 square kilometer (km2) 

Volume 

acre-foot (acre-ft) 1,233 cubic meter (m3) 

Velocity and flow 

foot per second (ft/s) 0.3048 meter per second (m/s) 

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s) 

cubic foot per second per square 0.01094 cubic meter per second per square 

mile [(ft3/s)/mi2] kilometer [(m3/s)/km2] 

Slope 

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km) 

Other Abbreviations 

CHWx-L Cold River high-water mark, left bank
 

CHWx-R Cold River high-water mark, right bank
 

FEMA Federal Emergency Management Agency
 

NOAA National Oceanic and Atmospheric Administration
 

NWS National Weather Service
 

USGS U.S. Geological Survey
 

WHWx-L Warren Brook high-water mark, left bank
 

WHWx-R Warren Brook high-water mark, right bank
 

In this report, the words “right” and “left” refer to directions that would be reported by an 

observer facing downstream. 

NAVD 88: In this report, “NAVD 88” refers to the North American Vertical Datum of 1988. 
Flood of October 8 and 9, 2005, on Cold River in 

Walpole, Langdon, and Alstead and on Warren Brook in 

Alstead, New Hampshire 

By Scott A. Olson 

Abstract 

Southwestern New Hampshire experienced damaging 

flooding on October 8 and 9, 2005. The flooding was the 

result of a storm producing at least 7 inches of rain in a 

30-hour period. The heavy, intense rainfall resulted in runoff 

and severe flooding, especially in regions of steep topography 

that are vulnerable to flash flooding. Some of the worst 

property damage was in the towns of Alstead, Langdon, 

and Walpole, New Hampshire along Cold River and Warren 

Brook. Warren Brook was severely flooded and had flows that 

exceeded a 100-year recurrence interval upstream of Cooper 

Hill Road. Downstream of Cooper Hill Road, the flooding 

was worsened as a result of a sudden release of impounded 

water, making the flood levels greater than what would be 

experienced from a 500-year recurrence-interval flood. 

Along Cold River, upstream of its confluence with 

Warren Brook, flooding was at approximately a 100-year 

recurrence interval. Downstream of the confluence of Cold 

River and Warren Brook, the streamflows, which were swollen 

by the surge of water from Warren Brook, exceeded a 500­

year recurrence interval. 

Introduction 

Major flooding occurred in southwestern New Hampshire 

on October 8 and 9, 2005, as a result of torrential rainfall. 

The flooding resulted in seven deaths—four of which were 

in Alstead, NH. More than 100 buildings or homes were 

damaged or destroyed. Many miles of roads in the region 

were damaged and remained impassable for days, even weeks, 

following the flood. 

On October 26, 2005, President George W. Bush declared 

a major disaster area in five counties in the State of New 

Hampshire as a result of widespread damage caused by the 

flooding. In response to this declaration, the U.S. Geological 

Survey (USGS), in cooperation with the Federal Emergency 

Management Agency, measured the high-water elevations, 

determined peak discharges as a result of the flooding, and 

estimated flood-flow frequency for selected watercourse 

areas affected by the flooding. The purpose of this report is to 

document the flood on Cold River in Walpole, Langdon, and 

Alstead, and on Warren Brook in Alstead, NH. Because of the 

severity of the flooding, the following communities and stream 

reaches were included in this report: (1) a 6.7-mi reach of 

Cold River from its mouth where it drains into the Connecticut 

River in Walpole, NH, to Vilas Pool Dam in Alstead, and (2) a 

4.5-mi reach of Warren Brook from its mouth where it drains 

into Cold River to Warren Lake in Alstead. 

Description of Investigated Reaches 

Cold River (fig. 1) flows southwesterly through Alstead, 

Langdon, and Walpole along a relatively steep slope, averaging 45 ft/mi, and drains into the Connecticut River at an 

elevation of about 230 ft. The headwaters of Cold River reach 

1,900 ft in elevation. Cold River is in the New England Upland 

physiographic region of southwestern New Hampshire. The 

drainage area of Cold River at its confluence with the 

Connecticut River is 102 mi2. 

Warren Brook (fig. 1) flows westerly through Alstead, 

draining into Cold River in steep topography. It is an upland 

stream, and is also in the New England Upland physiographic 

region. The elevation of the mouth of the Warren Brook is 

approximately 510 ft, and the headwaters extend to elevations 

above 1,500 ft. The average channel slope of the reach 

investigated is 150 ft/mi. The drainage area of Warren Brook 

at its confluence with Cold River is 12.5 mi2. 

Storm Characteristics 

The storm of October 8 and 9, 2005, produced at least 

7 in. of precipitation (National Weather Service Forecast 

Office, 2005) in southwestern New Hampshire. Unverified 

accounts indicated as much as 12 in. of rain fell in a 30-hour 

period (Sarah Liebowitz, Concord Monitor, written commun., 

October 20, 2005). The precipitation station at Keene, 

NH, operated by the National Oceanic and Atmospheric 

Administration, recorded 7.68 in. of rainfall from 
2 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH 

72o30' 72o15' 

43o15' 

43o00' 

Langdon 

Alstead 

Walpole 

Connectic u t R iver 

C o l d R i v e r 

Warren Brook 

Ashuelot River 

Gilsum 

Keene 

New 

Hampshire 

Vermont 

New Hampshire 

Base from U.S. Geological Survey 0 5 10 MILES 

Digital Line Graph, 1990, 1:24,000 and 

National Hydrography Dataset, 1999, 1:24,000 0 5 10 KILOMETERS 

Figure 1. Location of investigated reaches and the towns of Walpole, Langdon, and Alstead, NH. 
Peak-Discharge Estimates  

October 8 through 9, 2005 (National Weather Service Forecast 

Office, 2005). Prior to the storm, hydrologic conditions in the 

area were predominately normal (U.S. Geological Survey, 

2006). The heavy, intense rainfall resulted in runoff and severe 

flooding, especially in regions of steep topography that are 

vulnerable to flash flooding. 

High-Water Marks 

USGS personnel identified and flagged high-water marks 

along the investigated reaches of Cold River and Warren 

Brook following the flood. The high-water marks were tied 

into the North American Vertical Datum of 1988 (NAVD 88), 

using closed level-loop surveying techniques between October 31 and November 18, 2005. Latitude and longitude of the 

high-water marks were determined, using Global Positioning 

System instrumentation. 

The elevation and location of the high-water marks are 

described in tables 1 and 2 (back of report) and the locations 

are plotted on USGS orthophotos in appendix 1. The highwater marks also are plotted in profile format for each 

investigated reach in appendix 2. 

The high-water marks also are rated for accuracy. This 

rating is subjective and is based upon the type of high-water 

mark and the abundance of other confirming marks in the 

immediate vicinity (Benson and Dalrymple, 1967). The accuracy of the mark is defined as follows: A high-water mark 

having (1) an excellent rating is within 0.05 ft of the actual 

water surface, (2) a good rating is within 0.1 ft, (3) a fair rating 

is within 0.2 ft, and (4) a poor rating may be greater than 0.2 ft 

from the true peak water surface. 

Elevation reference marks used to establish the elevations 

of the high-water marks are reported in appendix 3. 

Peak-Discharge Estimates 

In addition to obtaining high-water marks, USGS 

personnel surveyed cross sections in select locations so that 

the surveyed geometry data and the high-water-mark elevation 

data could be used together in hydraulic models to estimate 

the peak discharges. Peak-discharge estimates, using these 

indirect techniques, were made in four locations: Warren 

Brook at Mill Hollow, Cold River at Vilas Pool Dam, Cold 

River downstream of the Warren Brook confluence, and Cold 

River at the Drewsville USGS stream-gaging station (fig. 2). 

The peak-discharge estimates are discussed in upstream to 

downstream order. 

Peak-discharge estimates of Warren Brook downstream 

of Cooper Hill Road (fig. 2) were made using a dam-breach 

model. This was used because of the nature of the failure 

of the Cooper Hill Road embankment that impounded 

flood waters. 

Warren Brook at Mill Hollow 

An indirect discharge measurement was made at the 

Route 123 crossing of Warren Brook at Mill Hollow. Although 

the Mill Hollow site has complex hydraulics, the site was 

selected because excellent high-water-mark elevations were 

available and the dam and culvert incurred minimal damage 

during the flooding. At the Mill Hollow site, the surveyed 

geometry of the dam, the Route 123 culvert, Route 123 

roadway, and an approach cross section were input into the 

U.S. Army Corps of Engineers (2004) HEC-RAS program. 

Discharges were iteratively selected so that the resulting watersurface elevations output from HEC-RAS at the approach 

section matched the high-water marks surveyed upstream of 

the site. The resulting peak discharge for the October 2005 

flood event was 820 ft3/s for the 5.21-mi2 drainage area. 

Warren Brook Downstream of Cooper Hill Road 

Peak-discharge estimates were determined immediately 

downstream of the Cooper Hill Road crossing of Warren 

Brook. During the flood, the Cooper Hill Road embankment 

impounded flood waters flowing down Warren Brook. Using 

the National Elevation Dataset (U.S. Geological Survey, 

2001), the impoundment was computed to be 421 acre-ft 

of water. When the nearly 30-ft tall road embankment was 

overtopped, it breached, sending the entire impounded pool of 

floodwaters rushing downstream. 

Because of the apparent similarities of the impoundment failure to an earthen dam failure, the National Weather 

Service’s Simplified Dam-Break (SMPDBK) Flood Forecasting Model (Wetmore and Fread, 1991) was used to estimate 

the peak discharges downstream of the breached road embankment. The geometry of the breached road embankment was 

surveyed and used as input along with the impoundment 

volume. Additional cross sections downstream of the Cooper 

Hill Road crossing along Warren Brook to its mouth were 

estimated from the USGS 1:24,000 topographic map (U.S. 

Geological Survey, 1998a) and also used as input to the model. 

The additional cross sections allowed the SMPDBK model 

to route the peak discharge down Warren Brook to its mouth 

where it drains into Cold River. 

The discharges computed by the SMPDBK model were 

sensitive to the amount of time that the road embankment was 

given to completely breach. The breach occurred in about a 

20- to 30-minute timeframe (David Crosby, town of Alstead 

Director of Public Works, oral commun., December 19, 2005). 

Thus, a breach time of 25 minutes was used in the model. The 

results from SMPDBK indicate a peak discharge immediately 

downstream of Cooper Hill Road of 24,900 ft3/s and a peak 

discharge of 20,100 ft3/s at the confluence with Cold River. 

Decreasing the time to 20 minutes increased peak discharges 

by approximately 7 percent; increasing the breach time to 

30 minutes decreased peak discharges by about 3 percent. 
72o25' 72o20' 

43o10' 

#

#

#

#

!

!

!

#

!

##

Langdon 

Walpole 

Alstead 

Charlestown 

Acworth 

12A 

12A 

123 

123A 

W arr en

Lak e 

Warren Brook 

Cold River 

Cold River 

Cold River 

Cold River at confluencewith Connecticut Ri ver 

Cold River at DrewsvilleU .S. Geological Surveystream-g aging station

Cold River at McDermott Bridge 

Cold River at Route 123 bridge in village of Alstead 

Cold Riverdownstream ofconfluence with

Warren Brook 

Warren Brookat confluencewith Cold Ri ver 

Cold River at 

Vilas Pool Dam

Warren Brook downstreamof Cooper Hill R oad 

Warren Brookat Mill Hollow 

C o n n e c t i c u t R i v e r 

123 

Area of water impounded byCooper Hill R oad embankment Peak-discharge and flood-flowfrequency estimatedPeak-discharge estimate attemptedFlood-flow frequency estimated 

0 1 2 MILES 0 1 2 KILOMETERS 

VT 

Cooper Hill Road 

 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH 43o05'

Figure 2. Locations where peak discharge and flood-flow frequency were estimated in Walpole, Langdon, and Alstead, NH. 
Peak-Discharge Estimates 5 

Photograph courtesy of Reggie Clark, Alstead, NH 

Figure . View looking upstream at the Cooper Hill Road embankment failure October 2005 in Alstead, NH. 
 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH 

Cold River at Vilas Pool Dam 

An indirect discharge measurement was made for Cold 

River at Vilas Pool Dam. The site is not considered ideal for 

an indirect discharge measurement as described by Hulsing 

(1967) because a large percentage of the flow is diverted 

over Route 123A adjacent to the dam. The flow over Route 

123A and Vilas Pool Dam were modeled as a broad-crested 

weir. The geometry of the dam, the Route 123A overflow 

section, and an approach cross section were surveyed and 

input into the U.S. Army Corps of Engineers (2004) HECRAS program. Discharges were iteratively selected so that the 

resulting water-surface elevations output from HEC-RAS at 

the approach section matched the high-water-mark elevations 

at the approach section at Vilas Pool Dam. The resulting peak 

discharge was 6,370 ft3/s for the 61.3-mi2 drainage area. 

Cold River Downstream of the Warren Brook 

Confluence 

An indirect discharge measurement was attempted on 

Cold River downstream of the Warren Brook confluence 

(fig. 2). However, an acceptable indirect discharge could not 

be generated because of complex hydraulics. 

Cold River at the Drewsville USGS StreamGaging Station 

An indirect discharge measurement was made for the 

discontinued USGS stream-gaging station, Cold River at 

Drewsville, NH, station number 01155000. The streamgage is 

located about 60 ft upstream of the Route 123 crossing of 

Cold River in Drewsville and has a drainage area of 82.7 mi2. 

Continuous record was collected at the station from 1940 to 

1978. During the period of record, the maximum recorded 

discharge was 6,710 ft3/s on December 21, 1973 (U.S. Geological Survey, 1978). The corresponding maximum stage was 

12.30 ft, which when converted to NAVD 88 is 390.58 ft. The 

October 9, 2005, peak stage was 401.98 ft, or 11.40 ft higher 

than the peak stage of December 21, 1973. 

The reach used for the indirect discharge measurement 

was a straight section of river with a broad flood plain left 

of the channel starting at about 2,500 ft upstream of the 

station. The reach met all the criteria for an indirect discharge 

measurement using the Slope-Area method as described in 

Dalrymple and Benson (1967). Three cross sections were 

surveyed and used as input into the Slope-Area Computation 

program (Fulford, 1994) along with the corresponding highwater elevations. The resulting peak discharge was estimated 

to be 21,800 ft3/s. The wide flood plains downstream of the 

Village of Alstead and upstream of the reach used for the 

indirect measurement may have attenuated some of the flood 

wave from the breached Cooper Hill Road embankment on 

Warren Brook. 

Flood-Flow-Frequency Characteristics 

The flood-flow-frequency estimates are discussed 

in upstream to downstream order. Flood-flow frequency 

estimates for Warren Brook were estimated using regression 

equations developed by LeBlanc (1978) (table 3, fig. 4). 

Basin characteristics used as input to the regression equations 

include drainage area, mean channel slope, and the 2-year, 

Table . Basin characteristics and flood-flow frequency estimates for selected recurrence intervals at selected sites on Warren 

Brook, Alstead, NH. 

[Location of sites shown in figure 2. Flood-flow frequency estimates plotted against drainage area are in figure 4. ft3/s, cubic feet per second; ft/mi, feet per 

mile; hr, hour; in., inches; mi2, square mile; yr, year] 

Flood-flow frequency estimates for selected Drainage Channel 2-yr, 2-hr recurrence intervals,

Warren Brook site area, slope, rainfall, ft

/s

mi2 ft/mi in. 

10 yr 50 yr 100 yr 500 yr 

Mill Hollow 5.21 101 2.7 289 508 615 958 

Downstream of Cooper Hill Road 9.24 147 2.7 629 1,140 1,380 2,190 

Confluence with Cold River 12.5 125 2.7 805 1,430 1,740 2,710 
Flood-Flow-Frequency Characteristics  

3,000 

DISCHARGE, IN CUBIC FEET PER SECOND 

2,800 

2,600 

2,400 

2,200 

2,000 

1,800 

1,600 

1,400 

1,200 

1,000 

800 

600 

400 

200 

0 

4 5 6 7 8 9 10 11 12 13 

DRAINAGE AREA, IN SQUARE MILES 

EXPLANATION 

Flood-flow frequency estimates 

for selected recurrence intervals 

10 year 

50 year 

100 year 

500 year 

Figure . Flood-flow frequency estimates for selected recurrence intervals at selected sites on Warren Brook, Alstead, 

NH. Location and information for selected sites are shown in figure 2 and table 3 (outlet of Lake Warren is represented by 

the first data points but values are not shown on table 3). 
8 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH 

24-hour rainfall for the basin. Drainage area and mean channel 

slope were determined using a Geographic Information 

System, electronic copies of USGS 1:24,000 topographic 

maps (U.S. Geological Survey, 1998a–d) and the National 

Elevation Dataset (U.S. Geological Survey, 2001). The 2-year, 

24-hour rainfall was determined from a rainfall-frequency 

atlas (Hershfield, 1961). These data sources for the basin 

characteristics are nearly identical to the data sources used to 

derive the LeBlanc regression equations. 

Flood discharges at the 10-, 50-, 100-, and 500-year 

recurrence intervals for Cold River at Drewsville were determined using a log-Pearson Type III analysis (U.S. Interagency 

Advisory Committee on Water Data, 1982). Peak-flow data 

from Cold River at Drewsville, NH, stream-gaging station 

were used for computing the frequency curve. The October 

2005 peak was adjusted to a “natural” peak—without the 

effect of the embankment breach on Warren Brook. 

Several approaches were investigated to determine a 

natural peak at Cold River station. The first approach involved 

applying the peak runoff rate in cubic feet per second per 

square mile for this flood from the nearby Ashuelot River 

(fig. 1), as a way to estimate the natural peak on Cold River. 

The peak discharge of the Ashuelot River at the discontinued 

Gilsum, NH, USGS stream-gaging station was determined to 

be 10,200 ft3/s using the Slope-Area technique (Dalrymple 

and Benson, 1967). The drainage area at the Ashuelot River 

at Gilsum, NH, station is 71.1 mi2, resulting in a 143-ft3/mi2 

runoff rate for the peak discharge. The drainage area of 

Cold River at Vilas Pool Dam (61.3 mi2) had a peak runoff 

rate, however, of 104 ft3/mi2; applying the runoff rate of the 

Ashuelot River to Cold River likely would have resulted in an 

overestimate of the natural peak flow. 

Another approach was to apply the 104-ft3/mi2 runoff rate 

from Vilas Pool Dam to Cold River at the Drewsville site. The 

runoff rate at Warren Brook at Mill Hollow was much greater 

at 158 ft3/mi2; however, applying the lower Vilas Pool Dam 

runoff rate may result in an underestimate of the peak flow. 

It was determined that the best approach to determine a 

natural peak was to use a drainage-area-weighted runoff rate 

using the Warren Brook runoff rate and Cold River at Vilas 

Pool Dam runoff rate. This weighted approach resulted in a 

runoff rate of 113 ft3/mi2. Applying this runoff rate to Cold 

River at Drewsville stream-gaging station drainage area of 

82.7 mi2 resulted in a rate of 9,360 ft3/s. This rate was the 

natural peak-discharge estimate that was included in the 

log-Pearson Type III analysis. The results of the frequency 

analysis are shown in table 4 and figure 5. The frequency 

curve then was adjusted to locations upstream and downstream 

of the station by applying a drainage-area ratio. For example, 

Q=Qgage(A/Agage), where Qgage and Agage are the discharge and drainage area of the station and Q and A are the 

discharge and drainage area of the site of interest, respectively. 

Table . Flood-flow frequency estimates for selected recurrence intervals at selected sites on Cold River, southwestern 

New Hampshire, 2005. 

[Location of sites shown in figure 2. Flood-flow frequency estimates plotted against drainage area are shown in figure 5. ft3/s, cubic feet per second; mi2, square 

mile; yr, year] 

Cold River site Drainage area, 

mi2 

Flood-flow frequency estimates for selected recurrence intervals, 

ft/s 

10 yr 50 yr 100 yr 500 yr 

McDermott Bridge, Langdon, NH 59.2 2,930 4,910 5,980 9,090 

Vilas Pool Dam, Alstead, NH 61.3 3,030 5,080 6,190 9,410 

Route 123 bridge in Village of Alstead, NH 74.6 3,690 6,190 7,530 11,500 

Cold River at Drewsville, NH, USGS stream­ 82.7 4,090 6,860 8,350 12,700 

gaging station 

Confluence with the Connecticut River 102 5,040 8,460 10,300 15,700 
Flood-Flow-Frequency Characteristics 9 

16,000 

DISCHARGE, IN CUBIC FEET PER SECOND 

14,000 

12,000 

10,000 

8,000 

6,000 

4,000 

2,000 

0 

55 60 65 70 75 80 85 90 95 100 105 

DRAINAGE AREA, IN SQUARE MILES 

EXPLANATION 

Flood-flow frequency estimates 

for selected recurrence intervals 

10 year 

50 year 

100 year 

500 year 

Figure 5. Flood-flow frequency estimates for selected recurrence intervals at selected sites on Cold River, Alstead, 

Langdon, and Walpole, NH. Location and information for selected sites are shown in figure 2 and table 4. 
10 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH 

Summary of flood-flow frequency estimates and peak-discharge estimates of the October 2005 flood at selected locations in Walpole, 

Langdon, and Alstead, NH. 

[ft3/s, cubic feet per second; mi2, square miles; yr, year; --, no data; >, greater than; ~, approximately] 

Flood-flow frequency estimates for selected 

Location 

Drainage 

area, 

mi2 

10 yr 

recurrence intervals, 

ft/s 

50 yr 100 yr 500 yr 

Peak 

discharge, 

October 2005, 

ft/s 

Recurrence 

interval 

of peak 

discharge 

Warren Brook 

At Mill Hollow, Alstead, NH 5.21 289 508 615 958 820 >100-year 

Downstream of 9.24 629 1,140 1,380 2,190 24,900 >500-year 

Cooper Hill Road, Alstead, NH 

At confluence with Cold River, Alstead, NH 12.5 805 1,430 1,740 2,710 20,100 >500-year 

Cold River 

At McDermott Bridge, Langdon, NH 59.2 2,930 4,910 5,980 9,090 -- --

At Vilas Pool Dam, Alstead, NH 61.3 3,030 5,080 6,190 9,410 6,370 ~100-year 

At Route 123 bridge in Village of Alstead, NH 74.6 3,690 6,190 7,530 11,500 -- --

At Cold River at Drewsville, NH, USGS stream­ 82.7 4,090 6,860 8,350 12,700 21,800 >500-year 

gaging station 

At confluence with Connecticut River, 102 5,040 8,460 10,300 15,700 -- --

Walpole, NH 

Summary 

The U.S. Geological Survey, in cooperation with the 

Federal Emergency Management Agency, surveyed highwater marks along the flooded reaches of Cold River in 

Alstead, Langdon, and Walpole, NH, and Warren Brook 

in Alstead, NH, to document the flood of October 8 and 

9, 2005. Discharge estimates also were made in selected 

locations along these reaches. The peak discharges in Warren 

Brook downstream of Cooper Hill Road and in Cold River 

downstream of the confluence of Cold River and Warren 

Brook are attributed to the failure of a road embankment 

that released 421 acre-feet of impounded water in a 20- to 

30-minute timeframe. New flow-frequency curves were 

determined for the investigated reaches as well. 

Selected References 

Benson, M.A., and Dalrymple, Tate, 1967, General field and 

office procedures for indirect discharge measurements: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 3, chap. A1, 30 p. 

Bodhaine, G.L., 1968, Measurement of peak discharge at 

culverts by indirect methods: U.S. Geological Survey 

Techniques of Water-Resource Investigations, book 3, 

chap. A3, 60 p. 

Dalrymple, Tate, and Benson, M.A., 1967, Measurement of 

peak discharge by the slope-area method: U.S. Geological 

Survey Techniques of Water-Resource Investigations, 

book 3, chap. A2, 12 p. 
11 

Federal Emergency Management Agency, 2000, Flood insurance study, Town of Walpole, Cheshire County, New Hampshire: Washington, DC, p. 16. 

Fulford, J.M., 1994, User’s guide to SAC, A computer program for computing discharge by slope-area method: U.S. 

Geological Survey Open-File Report 94–360, 31 p. 

Hershfield, D.M., 1961, Rainfall frequency atlas of the United 

States for durations from 30 minutes to 24 hours and return 

periods from 1 to 100 years: U.S. Department of Commerce Weather Bureau Technical Paper No. 40, 61 p. 

Hulsing, Harry, 1967, Measurement of peak discharge at dams 

by indirect methods: U.S. Geological Survey Techniques of 

Water-Resource Investigations, book 3, chap. A5, 29 p. 

LeBlanc, D.R., 1978, Progress report on hydrologic investigations of small drainage areas in New Hampshire—Preliminary relations for estimating peak discharges on rural, 

unregulated streams: U.S. Geological Survey WaterResources Investigations 78–47, 9 p. 

National Weather Service Forecast Office, 2005, Daily 

climate data, accessed December 20, 2005, at 

http://www.erh.noaa.gov/er/box/dailystns.shtml. 

U.S. Army Corps of Engineers, 2004, HEC-RAS River 

Analysis System Version 3.1.2: Hydrologic Engineering 

Center, accessed October 26, 2004, at 

http://www.hec.usace.army.mil/. 

U.S. Geological Survey, 1978, Water resources data for New 

Hampshire and Vermont, water year 1978: U.S. Geological 

Survey Water-Data Report NH-VT-78-1, 188 p. 

Selected References 

U.S. Geological Survey, 1998a, Alstead, New Hampshire 

7.5-minute series quadrangle map: U.S. Geological Survey 

Topographic Maps, scale 1:24,000. 

U.S. Geological Survey, 1998b, Bellows Falls, VermontNew Hampshire 7.5-minute series quadrangle map: U.S. 

Geological Survey Topographic Maps, scale 1:24,000. 

U.S. Geological Survey, 1998c, Gilsum, New Hampshire 

7.5-minute series quadrangle map: U.S. Geological Survey 

Topographic Maps, scale 1:24,000. 

U.S. Geological Survey, 1998d, Walpole, New HampshireVermont 7.5-minute series quadrangle map: U.S. Geological Survey Topographic Maps, scale 1:24,000. 

U.S. Geological Survey, 2001, National elevation dataset, 

accessed May 5, 2004, at http://edcnts12.cr.usgs.gov/ned/. 

U.S. Geological Survey, 2006, Water resources conditions in 

New Hampshire and Vermont September 2005, accessed 

April 21, 2006, at http://nh.water.usgs.gov/WaterData/2005/

sep05.htm. 

U.S. Interagency Advisory Committee on Water Data, 1982, 

Guidelines for determining flood flow frequency, Bulletin 

17-B of the Hydrology Subcommittee: Reston, VA, 

U.S. Geological Survey, Office of Water Data Coordination, 

183 p. 

Wetmore, J.N., and Fread, D.L., 1991, The National Weather 

Service simplified dam-break flood forecasting model 

(CD Rom with documentation): National Weather Service Hydrologic Research Laboratory, National Technical 

Information Service order no. PB 2003-500005, accessed 

December 2005, at http://www.NTIS.gov. 

Tables 1–2
 
Table 1. High-water elevations of the October 2005 flood on Cold River in Walpole, Langdon, and Alstead, NH.—Continued

[L, left; R, right; --, no data] 

Latitude/ Identifier Elevation1 Station2 longitude Description Rating 

CHW1-L 244.5 1,580 43 ̊7'17.1"/ Stake marking debris line 140 feet south of Route 123 bridge over Cold River at base of Route 123 road Excellent to good.

72 ̊25'35.7" embankment, at edge of corn field on left bank, and streamward of utility pole 51/3 

CHW2-L 248.5 1,836 43 ̊7'19.1"/ Spike marking grass/seed line in tree on left bank approximately 100 feet upstream of Route 123 bridge over Good to fair. 

72 ̊25'33.8" Cold River 

CHW3-L 249.7 2,583 43 ̊7'24.3"/ Spike, about 4 feet above ground, marking grass/seed line in 1-foot-diameter hemlock near bottom of road Good. 

72 ̊25'26.4" embankment left of Cold River 

CHW4-L 256.7 4,035 43 ̊7'35.4"/ Spike, about 5 feet above ground, marking grass/seed line in 18-inch-diameter oak tree streamward of Bre

w- Good. 

72 ̊25'16.5" ery Road and approximately 300 feet left of left bank of Cold River 

CHW5-L 402.0 18,487 43 ̊7'54.0"/ Mud line inside Cold River at Drewsville, NH. U.S. Geological Survey stream-gaging station on left bank of Excellent. 

72 ̊23'23.0" river upstream of Route 123 bridge 

CHW6-L 402.4 20,902 43 ̊7'54.6"/ Left flood plain -­

72 ̊23'0.1" 

CHW7-L 402.6 21,113 43 ̊7'56.5"/ Left flood plain -­

72 ̊22'58.4" 

CHW8-R 402.3 21,164 43 ̊8'1.4"/ Spike marking grass/seed line in 5-inch-diameter spruce tree approximately 40 feet downstream of a white 

Fair. 

72 ̊23'4.7" house and 75 feet right of right bank of Cold River 

CHW9-L 402.6 21,190 43 ̊7'57.1"/ Left flood plain -­

72 ̊22'58.1" 

CHW10-L3 402.0 21,341 43 ̊7'58.0"/ Left flood plain -­

72 ̊22'57.9" 

CHW11-R3 402.8 21,411 43 ̊8'1.2"/ Spike marking grass/seed line in 7-inch-diameter spruce tree approximately 100 feet upstream of a white 

Fair. 

72 ̊23'4.7" house and 45 feet right of right bank

CHW12-L3 403.8 21,521 43 ̊7'59.6"/ Debris line on left flood plain Poor. 

72 ̊22'56.7" 

CHW13-R 404.3 21,631 43 ̊8'3.1"/ Stake marking washline 50 feet right of right bank Good. 

72 ̊23'3.4" 

CHW14-L 403.9 21,678 43 ̊8'1.1"/ Debris line on left flood plain Poor. 

72 ̊22'55.6" 

CHW15-R3 405.2 21,782 43 ̊8'4.3"/ Spike marking grass/seed line in 6-inch-diameter deciduous tree near toe of Route 123 road embankment, 

Fair. 

72 ̊23'2.6" 50 feet right of right bank, and 30 feet upstream of a utility pole

CHW16-L 404.1 21,806 43 ̊8'2.7"/ Stake marking debris line 50 feet upstream of downstream end of corn field on left flood plain 

Fair. 

72 ̊22'55.0" 

CHW17-L3 406.1 21,881 43 ̊8'3.4"/ Left flood plain -­

72 ̊22'54.7" 

CHW18-L3 407.8 21,968 43 ̊8'4.1"/ Spike marking grass/seed line in 2-inch-diameter tree 5 feet bankward of treeline at edge of corn field on left Good to fair. 

72 ̊22'53.6" flood plain 

CHW19-R3 406.3 22,046 43 ̊8'6.6"/ Spike marking grass/seed line in 12-inch-diameter pine tree near toe of Route 123 road embankment and Good. 

72 ̊23'0.9" approximately 30 feet right of right bank of Cold River 

1 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH 
Table 1. High-water elevations of the October 2005 flood on Cold River in Walpole, Langdon, and Alstead, NH.—Continued

[L, left; R, right; --, no data] 

Latitude/ Identifier Elevation1 Station2 longitude Description	 Rating 

CHW20-L 408.4 22,070	 43 ̊8'5.0"/ Spike marking mudline on a 4-inch-diameter bankward leaning tree at the treeline at the bankward edge of Good. 

72 ̊22'53.0" field on left flood plain 

CHW21-L 408.3 22,306	 43 ̊8'6.8"/ Spike marking grass/seed line in 4-inch-diameter tree at the treeline at the bankward edge of field on left Good. 

72 ̊22'51.9" flood plain 

CHW22-R 407.7 22,327	 43 ̊8'9.2"/ Spike, about 4 feet above ground, marking grass/seed line in 8-inch-diameter maple tree near top of right Good. 

72 ̊22'59.4" bank, 50 feet downstream and 50 feet streamward of utility pole 52/111 

CHW23-L 408.4 22,361	 43 ̊8'7.3"/ Spike marking grass/seed line in a 8-inch-diameter dead tree at the treeline at the bankward edge of field of Good to fair. 

72 ̊22'51.7" left flood plain

CHW24-L 408.2 22,557	 43 ̊8'10.1"/ Left flood plain -­

72 ̊22'55.7" 

CHW25-R3 408.2 22,579	 43 ̊8'11.1"/ Spike, about 4 feet above ground, marking grass/seed line in 5-inch-diameter poplar tree 40 feet right of right Good to fair. 

72 ̊22'58.2" bank and streamward of utility pole 51/112 

CHW26-L3 408.5 22,591	 43 ̊8'9.0"/ Spike marking grass/seed line in 4-inch-diameter tree at the treeline at the bankward edge of field of left Fair. 

72 ̊22'51.4" flood plain 

CHW27-R 411.1 22,771	 43 ̊8'12.5"/ Spike in 4-inch-diameter elm tree 15 feet right of right bank Fair. 

72 ̊22'57.0" 

CHW28-R 411.2 22,820	 43 ̊8'12.5"/ Spike marking grass/seed line in 10-inch-diameter elm tree 20 feet right of right bank and streamward of Fair to poor. 

72 ̊22'56.9" utility pole 55/50/113

CHW29-L 408.5 22,878	 43 ̊8'11.5"/ Stake marking debris line 40 feet streamward of treeline at edge of field of left flood plain Good. 

72 ̊22'50.6" 

CHW30-R 412.2 23,001	 43 ̊8'14.8"/ Stake marking washline on left bank 25 feet streamward of utility pole 117/49 Good. 

72 ̊22'56.1" 

CHW31-R 414.2 23,182	 43 ̊8'16.3"/ Spike, about 5 feet above ground, marking grass/seed line in 10-inch-diameter sycamore tree on right bank Excellent to good.

72 ̊22'54.7" 25 feet streamward of utility pole 48. May be affected by velocity head 

CHW32-L 411.1 23,278	 43 ̊8'13.7"/ Left flood plain -­

72 ̊22'48.2" 

CHW33-R 413.9 23,383	 43 ̊8'18.0"/ Stake marking debris line on right bank15 feet streamward of the edge of Route 123 and 30 feet upstream of Excellent. 

72 ̊22'52.5" downstream end of mowed area between Cold River and Route 123 

CHW34-L 414.5 23,675	 43 ̊8'15.9"/ Spike marking grass/seed line in 4-inch-diameter birch tree at treeline at edge of field on left flood plain Fair. 

72 ̊22'45.3" 

CHW35-R 416.6 23,894	 43 ̊8'20.7"/ Stake marking washline on right bank 25 feet streamward of the edge of Route 123 and near the downstream -­

72 ̊22'47.1" end of guardrail at upstream end of mowed area between Cold River and Route 123 

CHW36-L 415.3 23,982	 43 ̊8'17.9"/ Spike marking grass/seed line in 2-inch-diameter birch tree at treeline at edge of field on left flood plain Fair. 

72 ̊22'42.2" 

CHW37-R 424.5 24,652	 43 ̊8'25.5"/ Spike marking grass/seed line in 14-inch-diameter pine tree on right bank streamward of utility pole 127/41 -­

72 ̊22'39.6" 

CHW38-R 434.9 26,402	 43 ̊8'31.2"/ Spike marking grass/seed line in 2-foot-diameter poplar tree 25 feet right of right bank and streamward of Good. 

72 ̊22'23.9" Connecticut River bank 

Table 1 15
 
Table 1. High-water elevations of the October 2005 flood on Cold River in Walpole, Langdon, and Alstead, NH.—Continued

[L, left; R, right; --, no data] 

Latitude/ Identifier Elevation1 Station2 longitude Description Rating 

CHW39-R 447.5 27,976 43 ̊8'45.0"/ Spike marking grass/seed line in 1-foot-diameter oak tree on right flood plain 30 feet streamward of Route Good. 

72 ̊22'12.6" 123 and 80 feet downstream of utility pole 23 

CHW40-R 454.8 28,952 43 ̊8'52.0"/ Spike marking seed line in apple tree on right flood plain upstream of driveway to house at 75 River Street Good. 

72 ̊22'1.8" 

CHW41-R 465.1 29,874 43 ̊8'54.3"/ Spike marking grass/seed line in apple tree on right flood plain 30 feet streamward of utility pole 6 

Fair. 

72 ̊21'50.8" 

CHW42-L 467.1 30,300 43 ̊8'54.6"/ Spike in 8-inch-diameter pine tree 24 feet bankward of the Library Avenue and 20 feet upstream of utility Excellent. 

72 ̊21'43.8" pole 4/26 

CHW43-L 477.4 30,650 43 ̊8'56.6"/ Spike marking grass/seed line in trunk of spruce tree near the southeast corner of the Shedd-Porter Library in Good. 

72 ̊21'41.6" Alstead 

CHW44-L 480.4 31,066 43 ̊8'58.5"/ Spike, about 1 foot above ground, marking grass/seed line in 18-inch-diameter maple tree about 50 feet Excellent. 

72 ̊21'36.1" upstream of the upstream side of the Alstead Municipal building and 25 feet streamward of the Municipal 

building parking lot 

CHW45-L 480.4 31,359 43 ̊8'59.1"/ Line on stake, driven into Route 123 streamward road embankment, 60 feet upstream of entrance to cem- Excellent. 

72 ̊21'33.0" etery, 18 feet streamward of the edge of Route 123, and across Route 123 from utility pole 6 

CHW46-L 486.7 32,116 43 ̊9'1.6"/ Debris line on lawn across Route 123 from entrance to Alstead elementary school and upstream of 5 Forest Good. 

72 ̊21'23.8" Road 

CHW47-L 492.3 32,666 43 ̊9'2.2"/ Spike, about 1 foot above ground, marking grass/seed line in a 6-inch-diameter tree near top of left bank, 10 Poor. 

72 ̊21'17.6" feet downstream of a stone retaining wall and 6 feet bankward of downstream end of retaining wall 

CHW48-L 514.9 33,381 43 ̊9'2.4"/ Spike marking grass/seed line in 6-inch-diameter oak tree on left bank Poor. 

72 ̊21'9.5" 

CHW49-L 514.9 33,645 43 ̊9'2.8"/ Spike marking grass/seed line in 5-inch-diameter maple tree left of Route 123 near pool on opposite side of -­

72 ̊21'4.5" Route 123 from Cold River and about 50 feet downstream of utility pole VZ24 

CHW50-R 3522.9 35,020 --/-- Debris line on right bank of Cold River approximately 100 feet downstream of Vilas Pool Dam -­CHW51-L 540.0 35,088 43 ̊9'12.9"/ Spike in tree left of Vilas Pool dam -­

72 ̊20'53.5" 

CHW52-L 542.0 35,128 43 ̊9'13.0"/ Spike, about 2 feet above ground, marking grass/seed line in 24-inch-diameter tree 25 feet left of Route Excellent. 

72 ̊20'52.7" 123A beside Vilas Pool Dam 

CHW53-L 3542.1 35,238 43 ̊9'14.1"/ Spike marking grass/seed line in 2.5-foot-diameter pine tree on left side of Route 123A and about 120 feet Excellent. 

72 ̊20'52.0" upstream of Vilas Pool Dam 

1Elevations are in feet above the North American Vertical Datum of 1988.
2River distance in feet above mouth of the Cold River.
3High-water mark used in hydraulic model to estimate peak discharge.
 

1 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH 
Table 2. High-water elevations of the October 2005 flood on Warren Brook in Alstead, NH.—Continued

[L, left; R, right; --, no data] 

Latitude/ Identifier Elevation1 Station2 Longitude Description Rating 

WHW1-L 525.4 51 43 ̊9'3.8"/ Stake driven into ground marking debris line 150 feet left of intersection of Routes 123 and 123A -­

72 ̊21'2.5" 

WHW2-L 534.4 532 43 ̊9'5.2"/ Spike marking grass/seed line in 18-inch-diameter tree 50 feet left of road in front yard of 20 Forest Road Excellent. 

72 ̊20'55.5" (Route 123). A mud line inside yellow house across street from 20 Forest Road and 60 feet upstream of 

WHW2-L has an elevation of 535.1 feet 

WHW3-L 544.2 1,028 43 ̊9'5.9"/ Spike marking grass/seed line in 20-inch-diameter maple tree 35 feet left of Route 123, 80 feet upstream of Good. 

72 ̊20'48.9" unmarked utility pole, and on downstream side of drive leading up hill 

WHW4-L 545.3 1,085 43 ̊9'6.8"/ Spike, 7 feet above ground, marking grass/seed line in 7-inch-diameter hemlock 33 feet right of Route 123 Good. 

72 ̊20'48.2" in grove of coniferous trees 

WHW5-L 559.1 1,589 43 ̊9'7.2"/ Spike, 8 feet above ground, marking grass/seed line in 20-inch-diameter maple tree approximately 50 feet Good. 

72 ̊20'42.2" left of Route 123 and 75 feet downstream of 57 Forest Road (Route 123) 

WHW6-R 595.8 2,304 43 ̊9'7.3"/ Stake marking washline at top of ledge falls and right of channel Poor. 

72 ̊20'34.7" 

WHW7-R 611.4 2,678 43 ̊9'6.8"/ Spike marking grass/seed line in 20-inch-diameter spruce tree right of channel Fair to poor. 

72 ̊20'29.7" 

WHW8-R 631.3 3,408 43 ̊9'7.3"/ Spike marking grass/seed line in 6-inch-diameter yellow birch tree about 4 feet above base of tree. Tree is Fair. 

72 ̊20'21.6" right of channel across Warren Brook from a blue house 

WHW9-R 634.6 3,666 43 ̊9'5.3"/ Spike marking grass/seed line in base of 4-inch-diameter white pine tree right of channel and across Warren Fair. 

72 ̊20'18.7" Brook from automotive garage 

WHW10-R 636.2 3,760 43 ̊9'4.3"/ Spike marking grass/seed line in 4-inch-diameter white birch tree right of channel and across Warren Brook Good to fair. 

72 ̊20'17.8" from downstream side of brown house at 119 Forest Road 

WHW11-L 641.5 3,899 43 ̊9'2.1"/ Stake driven into ground marking debris line across Route 123 from 119 Forest Road Good. 

72 ̊20'21.6" 

WHW12-R 660.5 4,831 43 ̊8'58.7"/ Spike marking grass/seed line in 15-inch-diameter tree about 100 feet west of Griffin Hill Road bridge over Excellent. 

72 ̊20'10.5" Warren Brook and immediately downstream of a tributary to Warren Brook 

WHW13-R 665.2 5,136 43 ̊8'57.4"/ Spike, about 7 feet above ground, marking grass/seed line in 5-inch-diameter tree 35 feet right of right bank Good. 

72 ̊20'6.4" of Warren Brook and approximately 175 feet east of Griffin Hill Road bridge over Warren Brook 

WHW14-R 681.3 6,008 43 ̊8'51.8"/ Spike marking grass/seed line in 10-inch-diameter apple tree approximately 275 feet east of Route 123 Excellent. 

72 ̊19'56.9" bridge over Warren Brook and 60 feet downstream of house at 211 Forest Road 

WHW15-L 684.0 6,057 43 ̊8'50.3"/ Spike marking grass/seed line in base of 3-foot-diameter oak tree on left bank approximately 200 feet up- Poor. 

72 ̊20'0.0" stream of Route 123 bridge over Warren Brook 

WHW16-R 697.0 6,685 43 ̊8'48.9"/ Spike, about 8 feet above ground, marking grass/seed line on streamward side of a 3-foot-diameter pine tree Excellent. 

72 ̊19'51.5" 60 feet right of right bank and 20 feet downstream of small tributary 

WHW17-L 694.9 6,715 43 ̊8'47.5"/ Spike marking grass/seed line in base of 24-inch-diameter oak tree on left bank across Warren Brook from Fair. 

72 ̊19'52.0" downstream end of a greenhouse 

WHW18-L 706.2 7,393 43 ̊8'46.4"/ Spike, about 3 feet above ground, marking grass/seed line on a 10-inch-diameter maple tree on left overbank Fair. 

72 ̊19'43.8" across Warren Brook and 50 feet upstream of a red and brown gambrel style home 

Table 2 1 
18 

Table 2. High-water elevations of the October 2005 flood on Warren Brook in Alstead, NH.—Continued[L, left; R, right; --, no data] 

Latitude/ Identifier Elevation1 Station2 Longitude Description	 Rating 

WHW19-R 714.2 7,727	 43 ̊8'46.8"/ Spike marking grass/seed line in 2-foot-diameter pine tree 25 feet right of Route 123 and 120 feet upstream Excellent. 

72 ̊19'38.7" of utility pole 1/35

WHW20-L 712.6 7,764	 43 ̊8'45.3"/ Spike, about 5 feet above ground, marking grass/seed line on a 6-inch-diameter yellow birch tree on left 

Fair. 

72 ̊19'39.8" overbank across Warren Brook and 500 feet upstream of a red and brown gambrel style home 

WHW21-R 725.2 8,201	 43 ̊8'43.6"/ Base of stake driven into ground marking debris line 15 feet upstream along Warren Brook from a tributary Excellent. 

72 ̊19'33.1" to Warren Brook 

WHW22-L 726.1 8,361	 43 ̊8'41.0"/ Spike marking grass/seed line in base of 12-inch-diameter oak tree on top of left bank across Warren Brook Poor. 

72 ̊19'34.9" from a gray and blue house

WHW23-R 735.3 8,556	 43 ̊8'39.8"/ Spike, about 6 feet above ground, marking grass/seed line in 8-inch-diameter poplar tree about 150 feet right Good. 

72 ̊19'30.6" of Route 123 

WHW24-L 737.4 8,717	 43 ̊8'37.6"/ Spike marking grass/seed line in base of 8-inch-diameter spruce tree on left overbank 

Fair to poor. 

72 ̊19'33.6" 

WHW25-L 738.1 8,882	 43 ̊8'36.1"/ Spike marking grass/seed line in base of 20-inch-diameter white pine on left overbank approximately 

Fair to poor. 

72 ̊19'32.7" 200 feet downstream of a cluster of apple trees 

WHW26-R 740.1 8,950	 43 ̊8'36.6"/ Base of stake driven into ground marking debris line in grass near base of utility pole 53 in middle of large Good. 

72 ̊19'28.6" lawn right of Route 123 

WHW27-R 745.4 9,117	 43 ̊8'35.3"/ Spike marking grass/seed line in base of 2-foot-diameter maple tree 10 feet right of Route 123 and 50 feet Good. 

72 ̊19'28.8" downstream of driveway to house at 327 Forest Road 

WHW28-L 750.3 9,424	 43 ̊8'32.4"/ Spike marking grass/seed line in base of apple tree on left overbank on upstream edge of a field 

Fair. 

72 ̊19'32.5" 

WHW29-L 759.6 9,704	 43 ̊8'29.3"/ Spike marking grass/seed line in base of 20-inch-diameter spruce tree across Warren Brook from a mobile 

Fair to poor. 

72 ̊19'32.8" home damaged by the flood

WHW30-R 763.9 9,805	 43 ̊8'28.1"/ Stake driven into ground marking washline in grass on right side of Route 123 across street from utility pole 

Fair to poor. 

72 ̊19'29.2" VZ61 

WHW31-R 769.7 10,141	 43 ̊8'26.1"/ Spike marking grass/seed line in 10-inch-diameter oak tree 15 feet right of Route 123 and 60 feet upstream Good. 

72 ̊19'27.9" of utility pole 62

WHW32-R 778.8 10,340	 43 ̊8'23.9"/ Spike marking grass/seed line in 5-inch-diameter maple tree 25 feet right of right bank of Warren Brook and Excellent. 

72 ̊19'29.4" 100 feet downstream of house at 380 Forest Road 

WHW33-R 776.5 10,412	 43 ̊8'23.8"/ Spike marking grass/seed line in 18-inch-diameter tree on left overbank and near intersection of Route 123 Excellent. 

72 ̊19'27.4" and driveway to house at 380 Forest Road 

WHW34-R 789.4 10,750	 43 ̊8'20.4"/ Spike marking grass/seed line in downstream side of 20-inch-diameter maple tree 7 feet right of right bank Good. 

72 ̊19'26.6" of Warren Brook and streamward of utility pole VZ66 

WHW35-R 788.9 11,012	 43 ̊8'18.8"/ Spike, about 2 feet above ground, marking grass/seed line in 5-inch-diameter oak tree 20 feet right of Route Excellent. 

72 ̊19'23.2" 123 and 150 feet upstream of utility pole VZ67

WHW36-R 803.1 11,404	 43 ̊8'14.5"/ Spike marking grass/seed line in 4-inch-diameter maple tree immediately right of Route 123 and near front Good. 

72 ̊19'21.1" yard of a white house

WHW37-R 806.1 11,602	 43 ̊8'12.9"/ Spike marking grass/seed line in 15-inch-diameter hemlock tree 50 feet right of right bank and 30 feet 

Fair. 

72 ̊19'21.5" downstream of utility pole 1/73/73 

Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH 
Table 2. High-water elevations of the October 2005 flood on Warren Brook in Alstead, NH.—Continued

[L, left; R, right; --, no data] 

Latitude/ Identifier Elevation1 Station2 Longitude Description	 Rating 

WHW38-R3 834.0 12,713	 43 ̊8'4.3"/ Spike marking grass/seed line in 15-inch-diameter spruce tree on right bank immediately streamward of Excellent to good.

72 ̊19'18.5" Route 123, and 275 feet upstream of the intersection of Cobb Hill Road and Route 123

WHW39-L 860.4 17,016	 43 ̊7'51.8"/ Spike marking grass/seed line in tree 240 feet upstream of Route 123 culvert over Warren Brook, 25 feet -­

72 ̊18'41.0" downstream of utility pole 102, and 18 feet streamward of road 

WHW40-L 1,196.3 23,107	 43 ̊7'23.4"/ Spike marking grass/seed line in base of apple tree 50 feet upstream of Route 123 culvert Good. 

72 ̊17'56.4" 

WHW41-L3 1,196.4 23,127	 43 ̊7'23.1"/ Spike, about 2 feet above ground, marking grass/seed line in tree 75 feet upstream of Route 123 culvert Fair. 

72 ̊17'56.0" 

WHW42-L 1,196.4 23,142	 43 ̊7'23.1"/ Spike, about 4 feet above ground, marking grass/seed line in tree 15 feet left of left bank Fair. 

72 ̊17'55.6" 

WHW43-L 1,196.4 23,159	 43 ̊7'22.7"/ Spike, about 3 feet above ground, marking grass/seed line in tree approximately 100 feet upstream of Excellent. 

72 ̊17'55.9" Route 123 culvert and 20 feet downstream of stone wall 

WHW44-L 1,196.5 23,188	 43 ̊7'22.5"/ Spike, about 2 feet above ground, marking grass/seed line in large tree along stone wall Good. 

72 ̊17'55.5" 

WHW45-L 1,196.5 23,267	 43 ̊7'21.7"/ Spike marking grass/seed line in base of large tree in horse field Good to fair. 

72 ̊17'54.6" 

WHW46-R 1,196.3 23,314	 43 ̊7'22.5"/ Spike, about 2 feet above ground, marking grass/seed line in 2-foot-diameter elm(?) tree along Pine Cliff Excellent. 

72 ̊17'53.1" Road road embankment and approximately 50 feet south of intersection of Pine Cliff Road and Route 123 

WHW47-L 1,196.6 23,485	 43 ̊7'20.6"/ Stake marking debris line near base of large white pine tree in horse field left of Warren Brook Fair. 

72 ̊17'53.9"

1Elevations are in feet above the North American Vertical Datum of 1988.
2Stream distance in feet upstream of mouth.
3High-water mark used in hydraulic model to estimate peak discharge.
 

Table 2 19
 

Appendixes 1–3
Appendix 1: Maps Showing Location of High-Water Marks 

Flagged in Walpole, Langdon, and Alstead, NH, Following the 

Flood of October 8 and 9, 2005

Figures in appendix 1 begin at the mouth of Cold River, proceed upstream along Cold River to confluence of Cold River and 

Warren Brook, and then proceed upstream along Warren Brook to Warren Lake.

22 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH
Figure 1-1.  Location of high-water marks along Cold River, Walpole, NH (map 1 of 7).

#

#

#

#

72°26' 72°25'30" 72°25'

43°07'30"

43°07'

Continued on map 2

Connecticut River Cold River 123

123

12

12

CHW4-L

CHW3-L

CHW2-L

CHW1-L

123

Channel centerlineHigh-water mark #

0

0

1,000 2,000 FEET

250 500 METERS

Appendix 1 23
Figure 1-2.  Location of high-water marks along Cold River, Walpole, and Langdon, NH (map 2 of 7).

#

72°25' 72°24'30" 72°24'

43°08'30"

43°08'

Continued on map 1

CHW4-L

123

Channel centerlineHigh-water mark

#

0

0

1,000 2,000 FEET

250 500 METERS

Continued on map 3

Cold River

24 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH
Figure 1-3.  Location of high-water marks, cross sections, and elevation benchmark along Cold River, Walpole, Langdon, and Alstead, NH (map 3 of 7).

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

#

#

#

##

#

#

#

#

#

#

#

#

#

#

$T

Figure 1-3. Location of high-water marks, cross sections, and elevation benchmark along Cold River, Walpole, Langdon, and Alstead, NH (map 3 of 7).

72°23' 72°22'30"

43°08'30"

43°08'

Continued on map 2

Continued on map 4 72°23'30"

Cold River

0

0

1,000 2,000 FEET

250 500 METERS

Channel centerlineCross sectionHigh-water markElevation benchmark

123

#

$

123

CHW5-L CHW6-L

CHW7-L

CHW9-L

CHW10-L

CHW12-L

CHW14-L

CHW16-L

CHW17-L

CHW18-L

CHW20-L

CHW21-L

CHW26-L

CHW23-L

CHW29-L

CHW34-L

CHW38-R

CHW37-R

CHW35-R

CHW33-R

CHW31-R

CHW30-R

CHW28-R

CHW27-R

CHW25-R

CHW22-R

CHW19-R

CHW15-R

CHW13-R

CHW11-R

CHW8-R

CHW36-L

CHW24-L

CHW32-L

Cold River

461-0100

Appendix 1 25
Figure 1-4.  Location of high-water marks and elevation benchmark along Cold River, Alstead, NH (map 4 of 7).

$

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

Figure 1-4. Location of high-water marks and elevation benchmark along Cold River, Alstead, NH(map 4 of 7).

72°22' 72°21'30"

43°08'30"

43°09'

Continued on map 3

0

0

1,000 2,000 FEET

250 500 METERS

Continued on map 5

Cold River

72°22'30"

Channel centerlineHigh-water markElevation benchmark

$

72°21'

123

123

C 22 USGS 1926

CHW38-R

#

CHW39-R

CHW40-R

CHW41-R

CHW42-L

CHW43-L

CHW44-L

CHW46-L

CHW45-L

CHW47-L

CHW48-L

WHW1-L

CHW49-L

26 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH
Figure 1-5.  Location of high-water marks and cross sections along Cold River and Warren Brook, Alstead, NH (map 5 of 7).

Figure 1-5. Location of high-water marks and cross sections along Cold River and Warren Brook, Alstead, NH (map 5 of 7).

72°21' 72°19'30"

43°09'30"

43°09'

Continued on map 4

Continued on map 6

72°20'30" 72°20'

C

dl o

RiverWarren Brook

Griffin Hill Road

WHW1-L

Channel centerlineCross sectionHigh-water mark

0

0

1,000 2,000 FEET

250 500 METERS

CHW49-L

#

CHW48-L

CHW50-R

WHW2-L

CHW51-L

CHW52-L

CHW53-L

123

123

# #

##

#

#

#

#

# # # # #

#

#

#

#

#

#

#

#

#

# #

#

#

#

#

#

#

#

#

#

WHW3-L WHW4-L

WHW5-L WHW6-R WHW8-R

WHW9-R

WHW10-R

WHW11-L

WHW12-R

WHW13-R

WHW14-R

WHW15-L

WHW17-L

WHW16-R

WHW19-R

WHW21-R

WHW23-R

WHW26-R

WHW27-R

WHW18-L

WHW20-L

WHW22-L

WHW24-L

WHW25-L

# WHW28-L

#

Vilas

Pool

123A

WHW7-R

Appendix 1 27
Figure 1-6.  Location of high-water marks along Warren Brook, Alstead, NH (map 6 of 7).

28 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

Confluence with 

 Camp Brook

Confluence with 

 Allen Brook

Channel centerlineCross sectionHigh-water mark

0

0

1,000 2,000 FEET

250 500 METERS

#

72°19' 72°18'30"

43°08'30"

43°08'

Continued on map 7

Continued on map 5 72°19'30"

×

×

#

#

#

#

#

#

#

123

123

Warren Brook

WHW23-R

WHW26-R

WHW27-R

WHW22-L

WHW24-L

WHW25-L

WHW28-L

WHW30-R

WHW31-R

WHW32-R

WHW39-L

WHW29-L

Cooper Hill Road

WHW33-R

WHW34-R

WHW35-R

WHW36-R

WHW37-R

WHW38-R

Warren Brook
Figure 1-7.  Location of high-water marks, cross sections, and elevation benchmark along Warren Brook, Alstead, NH (map 7 of 7).

#

###

#

#

#

$T

#

###

#

#

#

$

0

0

1,000 2,000 FEET

250 500 METERS

Channel centerlineCross sectionHigh-water markElevation benchmark

#

$

Figure 1-7. Location of high-water marks, cross sections, and elevation benchmark along Warren Brook, Alstead, NH (map 7 of 7).

72°18' 72°17'30"

43°07'30"

43°08'

Continued on map 6

72°18'30" 72°19'

123

123

Warren Brook

Warren Lake

Warren Brook

C 24 USGS 1926

WHW39-L

WHW40-L

WHW41-L, WHW42-L

WHW43-L, WHW44-L

WHW45-L

WHW47-L

WHW46-R

Pine Cliff Road

Appendix 1 29
Appendix 2: Profiles of the October 2005 Flood on Cold River and 

Warren Brook, Southwestern New Hampshire

Flood profiles in appendix 2 are in order from downstream to upstream. The Cold River flood profile is shown first, followed by the 

Warren Brook flood profile.

30 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH
Cold River profile

270

4,500

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

260

250

240

230

220

210

200

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000

CHW4-L

CHW3-L CHW2-L

CHW1-L

Route 123

EXPLANATION

CHW1-L 

 High-water profile, October 2005 flood

 Minimum channel elevation

 Bridge deck elevation

 Bridge low-steel elevation

Appendix 2 31

Figure 2-1.  Profiles for Cold River, Walpole, NH.
Cold River profile

430

22,500

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

420

410

400

390

380

370

360

18,000 18,500 19,000 19,500 20,000 20,500 21,000 21,500 22,000

CHW12-L

CHW7-L CHW5-L

Route 123

EXPLANATION

CHW5-L

 High-water profile, October 2005 flood

 Minimum channel elevation

 Location of cross section shown in figure 1-3

 Bridge deck elevation

 Bridge low-steel elevation

CHW11-R

CHW13-R

CHW15-R

CHW17-L CHW18-L

CHW20-L

CHW23-L

U.S. Geological Survey stream-gaging

 station, Cold River at Drewsville, NH

Continued on profile 2-3

32 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH

Figure 2-2.  Profiles for Cold River, Walpole, and Langdon, NH.
Cold River profile

450

27,000

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

440

430

420

410

400

390

380

22,500 23,000 23,500 24,000 24,500 25,000 25,5000 26,000 26,500

EXPLANATION

CHW24-L

 High-water profile, October 2005 flood

 Minimum channel elevation

 Location of cross section shown in figure 1-3

Continued on profile 2-4

Confluence with 

 Darby Brook

Continued on profile 2-2

CHW38-R

CHW37-R

CHW34-L

CHW33-R

CHW24-L

CHW30-R

CHW28-R

CHW35-R

×

Appendix 2 33

Figure 2-3.  Profiles for Cold River, Langdon and Alstead, NH.
Cold River profile

490

31,500

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

480

470

460

450

440

430

420

27,000 27,500 28,000 28,500 29,000 29,500 30,000 30,500 31,000

Continued on profile 2-5

Continued on profile 2-3

CHW44-L

CHW41-R

CHW45-L

CHW42-L

CHW43-L

CHW39-R

CHW40-R

EXPLANATION

CHW39-R

 High-water profile, October 2005 flood

 Minimum channel elevation

 Bridge deck elevation

 Bridge low-steel elevation

Route 123

 (village of Alstead)

34 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH

Figure 2-4.  Profiles for Cold River, Alstead, NH.
Cold River profile

550

36,000

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

540

530

520

510

500

490

480

31,500 32,000 32,500 33,000 33,500 34,000 34,500 35,000 35,500 Continued on profile 2-4

CHW46-L

CHW48-L

Vilas Pool dam

470

460

EXPLANATION

CHW46-L

 High-water profile, October 2005 flood

 Minimum channel elevation

 Location of cross section shown in figure 1-5

×

Confluence with 

 Warren Brook

CHW47-L

CHW49-L

CHW50-R

CHW51-L

CHW52-L CHW53-L

Appendix 2 35

Figure 2-5.  Profiles for Cold River, Alstead, NH.
Warren Brook profile

620

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

600

580

560

540

520

480

500

0 500 1,000 1,500 2,000 2,500 3,000Continued on profile 2-7 Confluence with Cold River

WHW1-L

EXPLANATION

WHW1-L 

 High-water profile, October 2005 flood

 Minimum channel elevation

 Bridge deck elevation

 Bridge low-steel elevation

Route 123

WHW2-L

WHW3-L

WHW4-L

WHW5-L

WHW6-R

WHW7-R

36 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH

Figure 2-6.  Profiles for Warren Brook, Alstead, NH.
Warren Brook profile

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

EXPLANATION

WHW8-R

 High-water profile, October 2005 flood

 Minimum channel elevation

 Bridge deck elevation

 Bridge low-steel elevation

720

700

680

660

640

620

580

3,000 3,500 4,000 4,500 5,000 5,500 6,000Continued on profile 2-8 Continued on profile 2-6

WHW8-R

WHW9-R

WHW12-R WHW13-R

WHW11-L

WHW10-R

600

Griffin Hill Road

Route 123

Appendix 2 37

Figure 2-7.  Profiles for Warren Brook, Alstead, NH.
38 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH

Figure 2-8.  Profiles for Warren Brook, Alstead, NH.

Warren Brook profile

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

760

720

700

760

680

620

6,000 6,500 7,000 7,500 8,000 8,500 9,000

640

740

Continued on profile 2-9

Continued on profile 2-7

EXPLANATION

WHW14-R 

 High-water profile, October 2005 flood

 Minimum channel elevation

WHW14-R

WHW21-R

WHW19-R

WHW18-L

WHW16-R

WHW15-L

WHW22-L

WHW23-R

WHW24-L

WHW25-L

WHW26-R
Warren Brook profile

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

840

800

780

760

740

700

9,000 9,500 10,000 10,500 11,000 11,500 12,000

720

820

Continued on profile 2-10

Continued on profile 2-8

EXPLANATION

WHW27-R 

 High-water profile, October 2005 flood

 Minimum channel elevation

WHW27-R

WHW30-R

WHW29-L

WHW34-R

WHW36-R

WHW28-L

WHW31-R

WHW32-R

WHW35-R

WHW37-R

Confluence with 

 Allen Brook

×

Appendix 2 39

Figure 2-9.  Profiles for Warren Brook, Alstead, NH.
Warren Brook profile

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

900

860

840

820

800

760

12,000 12,500 13,000 13,500 14,000 14,500 15,000

780

880

Continued on profile 2-11

Continued on profile 2-9

Cooper Hill Road

WHW38-R

EXPLANATION

WHW38-R

 High-water profile, October 2005 flood

 Minimum channel elevation

 Location of cross section shown in figure 1-6

 Road elevation

 Top of culvert

40 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH

Figure 2-10.  Profiles for Warren Brook, Alstead, NH.
Warren Brook profile

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

940

900

880

860

840

800

15,000 15,500 16,000 16,500 17,000 17,500 18,000

820

920

Continued on profile 2-12

Continued on profile 2-10

WHW39-L

EXPLANATION

WHW39-L

 High-water profile, October 2005 flood

 Minimum channel elevation

 Road elevation

 Top of culvert

Confluence with 

 Camp Brook

×

Route 123 culvert

Appendix 2 41

Figure 2-11.  Profiles for Warren Brook, Alstead, NH.
Warren Brook profile

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

950

900

800

18,000 18,500 19,000 19,500 20,000 20,500 21,000

850

1,100

1,150

1,050

1,000

Continued on profile 2-13

Continued on profile 2-11

Route 123

EXPLANATION

 Minimum channel elevation

 Temporary bridge deck elevation

 Temporary bridge low-steel elevation

42 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH

Figure 2-12.  Channel profile for Warren Brook, Alstead, NH.
Warren Brook profile

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

21,000 21,500 22,000 22,500 23,000 23,500 24,000

1,160

1,180

1,140

1,120

1,100

1,080

1,060

Continued on profile 2-14

EXPLANATION

 Minimum channel elevation

 Road elevation

 Top of culvert

Route 123 culvert

1,040

Continued on profile 2-12

1,200

Appendix 2 43

Figure 2-13.  Channel profile for Warren Brook, Alstead, NH.
Warren Brook profile

STREAM DISTANCE, IN FEET ABOVE MOUTH

ELEVATION, IN FEET (NAVD 88)

1,210

1,205

1,200

1,195

1,190

1,185

1,180

23,000 23,100 23,200 23,300 23,400 23,500 23,600

Route 123 culvert

1,175

1,170

Continued on profile 2-13

Warren Lake dam

EXPLANATION

WHW40-L

 High-water profile, October 2005 flood

 Minimum channel elevation

 Location of cross section shown in figure 1-7

 Bridge deck elevation

 Bridge low-steel elevation

 Road elevation

 Top of culvert

23,700 23,800 23,900

Pine Cliff Road culvert

Mill dam

Prentice Hill Road

WHW40-L WHW45-L WHW47-L

44 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH

Figure 2-14.  Profiles for Warren Brook, Alstead, NH.
Appendix 3: Elevation Benchmarks Along Cold River and 

Warren Brook, New Hampshire

Appendix 3 45
 Table 3-1.  Elevation reference marks along Cold River and Warren Brook.

Designation

Elevation, 

feet

(NAVD 88)1

Description

461-0100 391.70 Standard tablet stamped “461-0100” set in the top of the upstream end of the north abutment of the 

Route 123 bridge over Cold River in Drewsville, NH.

C 22 USGS 1926 477.28 Standard USGS Disk stamped “C 22 1926” set in the north concrete curb of the grass triangle formed by 

the road junctions of State Routes 12-A and 123 and Hill Road in Alstead, NH.

C 24 USGS 1926 1,190.35 Standard USGS Disk stamped “C 24 1926” set in a concrete dam and foundation to an old grist mill 

(circa 1767) 40 feet north from the center of State Route 123 and 525 feet northwest of the outlet of 

Warren Lake, Alstead, NH.

1

 North American Vertical Datum of 1988.

46 Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, NH
Prepared by Publications Service Center 1 

For more information concerning the research in this report, contact: 

Keith W. Robinson, Director 

U.S. Geological Survey 

New Hampshire-Vermont Water Science Center 

361 Commerce Way 

Pembroke, NH 03275 

or visit our Web site at: 

http://nh.water.usgs.gov 
Olson, S.A. —Flood of October 8 and 9, 2005, on Cold River in Walpole, Langdon, and Alstead and on Warren Brook in Alstead, New Hampshire— 

USGS Open-File Report 2006–1221