Prepared in cooperation with the New Jersey Department of Environmental Protection

Flood-Inundation Maps for the Saddle River in Ho-Ho-Kus 

Borough, the Village of Ridgewood, and Paramus Borough, 

New Jersey, 2013

Pamphlet to accompany

Scientific Investigations Map 3299

U.S. Department of the Interior

U.S. Geological Survey

Flood-Inundation Maps for the Saddle 

River in Ho-Ho-Kus Borough, the Village 

of Ridgewood, and Paramus Borough, 

New Jersey, 2013

By Kara M. Watson and Michal J. Niemoczynski

Prepared in cooperation with the

New Jersey Department of Environmental Protection 

Pamphlet to accompany

Scientific Investigations Map 3299

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Watson, K.M., and Niemoczynski, M.J., 2014, Flood-inundation maps for the Saddle River in Ho-Ho-Kus Borough, 

the Village of Ridgewood, and Paramus Borough, New Jersey, 2013: U.S. Geological Survey Scientific Investigations 

Map 3299, 10 p., 10 sheets, http://dx.doi.org/10.3133/sim3299.

ISSN 2329–132X (online)
iii

Acknowledgments

The authors wish to thank the New Jersey Department of Environmental Protection which has 

cooperated in the funding of this study. The New Jersey Department of Environmental Protection 

and the U.S. Army Corps of Engineers, New York District has provided the funding for the operation and maintenance of the streamgage used for this study. Special thanks are given to Natural 

and Technological Hazards Management Consulting, Inc., (NTHMC) for providing the hydraulic 

model for this study and to the National Weather Service for assistance with the USGS floodinundation mapping initiative.

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Study Area Description........................................................................................................................2

Previous Studies ...................................................................................................................................2

Constructing Water-Surface Profiles.........................................................................................................6

Hydrologic and Steady-State Flow Data...........................................................................................6

Topographic and Bathymetric Data...................................................................................................6

Energy-Loss Factors.............................................................................................................................6

Model Calibration and Performance .................................................................................................6

Development of Water-Surface Profiles...........................................................................................6

Inundation Mapping ......................................................................................................................................8

Saddle River, New Jersey, Flood-Inundation Maps on the Internet............................................8

Disclaimer for Flood-Inundation Maps .............................................................................................8

Uncertainties and Limitations Regarding Use of Flood-Inundation Maps ..................................8

Summary..........................................................................................................................................................9

References Cited..........................................................................................................................................10
iv

Sheets 

[Separate documents available online with this report at the U.S. Geological Survey Publications 

Warehouse (http://dx.doi.org/10.3133/sim3299)]

Sheets 1–10. Maps showing:

Flood-inundation of the Saddle River in Ho-Ho-Kus Borough, the Village of Ridgewood, 

and Paramus Borough, New Jersey, corresponding to a gage height and an elevation (NAVD 88) as listed below at the U.S. Geological Survey streamgage Saddle River 

01390500 at Ridgewood, New Jersey.

1. Gage height of 5.0 feet and an elevation of 75.8 feet 

2. Gage height of 6.0 feet and an elevation of 76.8 feet 

3. Gage height of 7.0 feet and an elevation of 77.8 feet 

4. Gage height of 8.0 feet and an elevation of 78.8 feet 

5. Gage height of 9.0 feet and an elevation of 79.8 feet 

6. Gage height of 10.0 feet and an elevation of 80.8 feet 

7. Gage height of 11.0 feet and an elevation of 81.8 feet 

8. Gage height of 12.0 feet and an elevation of 82.8 feet

9. Gage height of 13.0 feet and an elevation of 83.8 feet

10. Gage height of 14.0 feet and an elevation of 84.8 feet

Figures

1. Map showing location of study reach for Saddle River and location of 

U.S. Geological Survey streamgages, in New Jersey ....................................................................3

2. Map showing location of study reach and direction of flow for the Saddle River 

at Ridgewood, New Jersey ............................................................................................................5
v

Tables

1. U.S. Geological Survey streamgage information for Saddle River at Ridgewood, 

New Jersey....................................................................................................................................4

2. 10-, 2-, 1-, and 0.2-percent annual exceedance probability peak-discharge 

estimates, drainage areas, and percentage of total discharge for selected 

locations on the Saddle River in New Jersey (from Federal Emergency 

Management Agency, 2005)........................................................................................................4

3. Measured peak discharges and gage heights for selected peaks at the 

U.S. Geological Survey streamgage Saddle River at Ridgewood, New Jersey 

(station 01390500)..........................................................................................................................7

4. Estimated discharges, in cubic feet per second, for corresponding stages and 

water-surface elevations at selected locations along the Saddle River, Ridgewood, 

New Jersey....................................................................................................................................7

5. Occurrence of bridge inundation determined from simulated water-surface profiles 

corresponding to stages for the Saddle River at Ridgewood, New Jersey streamgage (USGS streamgage 01390500)...........................................................................................9

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.59 square kilometer (km2)

Flow rate

cubic foot per second (ft3

/s) 0.0283 cubic meter per second (m3/s)

Vertical coordinate information is referenced to either (1) stage, the height above an arbitrary 

datum established at a streamgage, or (2) elevation, the height above the North American 

Vertical Datum of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 

(NAD 83).

Flood-Inundation Maps for the Saddle River in Ho-Ho-Kus 

Borough, the Village of Ridgewood, and Paramus Borough, 

New Jersey, 2013

By Kara M. Watson and Michal J. Niemoczynski

Abstract

Digital flood-inundation maps for a 5.4-mile reach of the 

Saddle River in New Jersey from Hollywood Avenue in HoHo-Kus Borough downstream through the Village of Ridgewood and Paramus Borough to the confluence with Hohokus 

Brook in the Village of Ridgewood were created by the U.S. 

Geological Survey (USGS) in cooperation with the New 

Jersey Department of Environmental Protection (NJDEP). The 

inundation maps, which can be accessed through the USGS 

Flood Inundation Mapping Science Web site at http://water.

usgs.gov/osw/flood_inundation/, depict estimates of the areal 

extent and depth of flooding corresponding to selected water 

levels (stages) at the USGS streamgage on the Saddle River at 

Ridgewood, New Jersey (station 01390500). Current conditions for estimating near real-time areas of inundation using 

USGS streamgage information may be obtained on the Internet at http://waterdata.usgs.gov/nwis/uv?site_no=01390500

or at the National Weather Services (NWS) Advanced Hydrologic Prediction Service (AHPS) at http://water.weather.gov/

ahps2/hydrograph.php?wfo=okx&gage=rwdn4. 

In this study, flood profiles were computed for the stream 

reach by means of a one-dimensional step-backwater model. 

The model was calibrated by using the most current stagedischarge relation (March 11, 2011) at the USGS streamgage 

01390500, Saddle River at Ridgewood, New Jersey. The 

hydraulic model was then used to compute 10 water-surface 

profiles for flood stages at 1-foot (ft) intervals referenced to 

the streamgage datum, North American Vertical Datum of 

1988 (NAVD 88), and ranging from 5 ft, the NWS “action and 

minor flood stage”, to 14 ft, which is the maximum extent of 

the stage-discharge rating and 0.6 ft higher than the highest recorded water level at the streamgage. The simulated 

water-surface profiles were then combined with a geographic 

information system 3-meter (9.84-ft) digital elevation model 

derived from Light Detection and Ranging (lidar) data in order 

to delineate the area flooded at each water level.

The availability of these maps along with information on the Internet regarding current stage from the USGS 

streamgage provides emergency management personnel and 

residents with information that is critical for flood response 

activities, such as evacuations and road closures as well as for 

post-flood recovery efforts.

Introduction

The Boroughs of Ho-Ho-Kus and Paramus, and the Village of Ridgewood, are urban communities with estimated 

populations of 4,080, 24,950, and 26,340, respectively, and 

population densities of 2,350, 4,340, and 2,510 persons per 

square mile (U.S. Bureau of Census, 2012). These communities have experienced severe flooding numerous times, most 

notably in 2011 (Tropical Storm Irene), 1999 (Tropical Storm 

Floyd), and 1977. National Flood Insurance Program flood 

insurance claims for these communities were reported to be 

$2,896,000 in 2011; $3,130,000 in 1999; and $62,800 in 1977 

(New Jersey Department of Environmental Protection, State 

National Flood Insurance Program Coordinators Office, written commun., 2013). Most of the flood damages have occurred 

along the Saddle River, which flows through the Borough of 

Ho-Ho-Kus (Ho-Ho-Kus) and forms the boundary between the 

Borough of Paramus (Paramus), and the Village of Ridgewood 

(Ridgewood). Floodplains along the Saddle River are highly 

developed and contain a mix of residential and commercial 

structures.

Prior to this study, Ho-Ho-Kus, Paramus, and Ridgewood 

officials relied on several information sources (all of which 

are available on the Internet) to make decisions on how to 

best alert the public and mitigate flood damages. One source 

is the Federal Emergency Management Agency (FEMA) 

Flood Insurance Study (FIS) for Bergen County dated September 30, 2005 (Federal Emergency Management Agency, 

2005). A second source of information is the U.S. Geological Survey streamgage, Saddle River at Ridgewood, New 

Jersey (station 01390500), from which current and historical 

water levels (stage) can be obtained. A third source of floodrelated information is the National Weather Service (NWS) 

Advanced Hydrologic Prediction Service (AHPS), which also 

displays the USGS stage data from the Ridgewood streamgage 
2 Flood-Inundation Maps for the Saddle River in Ho-Ho-Kus Ridgewood, and Paramus, New Jersey, 2013

[National Weather Service, 2013 (http://water.weather.gov/

ahps2/hydrograph.php?wfo=okx&gage=rwdn4)]. Although 

the NWS forecasts flood stage at many USGS streamgages, it 

does not provide forecasts of flood stages at streamgages with 

small drainage areas, such as the Saddle River at Ridgewood. 

This is because the time between a precipitation-runoff event 

and peak streamflow in these small drainage areas is typically 

shorter in duration than the 6-hour time step used by the NWS 

for stage forecasts.

Although the current stage at a USGS streamgage is useful for residents in the immediate vicinity of that streamgage, 

it is of limited use to residents farther upstream or downstream 

because the water-surface elevation is not constant along the 

entire stream reach. A water level at a streamgage is difficult to 

translate to depth and areal extent of flooding at points distant 

from the streamgage. One way to address these informational 

gaps is to produce a library of flood-inundation maps that are 

referenced to the stages recorded at the USGS streamgage. 

By referring to the appropriate map, emergency responders can discern the severity of flooding (depth of water and 

areal extent), identify roads that are or will soon be flooded, 

and make plans for notification or evacuation of residents in 

harm’s way for some distance upstream and downstream from 

the streamgage. In 2013, the USGS, in cooperation with the 

New Jersey Department of Environmental Protection, conducted a project to produce a library of flood-inundation maps 

for the Saddle River at Ridgewood, New Jersey.

Purpose and Scope

The purpose of this report is to describe the development of a series of estimated flood-inundation maps for the 

Saddle River at Ridgewood, New Jersey, and to present the 

maps, which are also available on the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/

flood_inundation/.

The flood-inundation maps cover a 5.4-mile reach of the 

Saddle River from Hollywood Avenue in Ho-Ho-Kus, downstream along the boundary between Ridgewood and Paramus, 

to the confluence with Hohokus Brook in Ridgewood, (fig. 1). 

Maps were produced for water levels referenced to the stage 

at the USGS streamgage on Saddle River at Ridgewood 

(01390500) and ranging from 5 ft or approximately bank 

full, and 0.5 feet (ft) below the NWS “action and minor flood 

stage”, to 14 ft, which is the maximum extent of the stagedischarge relation at the USGS streamgage, and 0.6 ft higher 

than the maximum recorded water level at the streamgage. 

Action stage is the stage which when reached by a rising 

stream, lake, or reservoir represents the level at which the 

NWS or a partner/user needs to take some type of mitigation 

action in preparation for possible significant hydrologic activity (National Weather Service, 2013).

Tasks specific to development of the flood maps were 

(1) analysis of peak streamflow data from USGS station 

01390500 (table 1), (2) collection of topographic data for 

selected cross sections and geometric data for structures and 

bridges throughout the study reach, (3) estimation of energyloss factors (roughness coefficients) in the stream channel and 

floodplain, and verification of steady-flow data from previous 

studies, (4) computation of water-surface profiles by use of the 

U.S. Army Corps of Engineer’s HEC–RAS computer program 

(U.S. Army Corps of Engineers, 2010), (5) production of estimated flood-inundation maps at various stream stages by use 

of Esri ArcMap 10.0 application of ArcGIS (Environmental 

Systems Research Institute, Inc., 2010), and (6) preparation of 

the maps, as shapefile polygons that depict the areal extent of 

flood inundation and as depth grids that provide the depth of 

floodwaters, for display on the USGS Flood Inundation Mapping ScienceWeb site. 

Study Area Description

The Saddle River is in northeastern New Jersey in the 

Piedmont Physiographic Province (fig. 1). The drainage 

area ranges from 21.6 square miles (mi2) at the Saddle River 

at Ridgewood streamgage to 23.2 mi2 at the downstream 

extent of the study reach. The source of the Saddle River is 

13.2 miles upstream from the Saddle River at Ridgewood 

streamgage in Rockland County in southern New York State. 

The stream flows generally southward before entering the 

borough limits of Ho-Ho-Kus in Bergen County, New Jersey. 

No major tributaries flow into the Saddle River within the 

study reach. The Saddle River drains into the Passaic River 

22.8 miles downstream from the Saddle River at Ridgewood 

streamgage (fig. 1). The basin terrain is moderately hilly. The 

study reach is approximately 5.4-miles long, has an average 

top-of-bank channel width of about 90 ft and has an average channel slope of 10.6 feet per mile. About 78 percent of 

the land contiguous to the study reach is classified as urban 

or developed, 14 percent as forest, and 1 percent as wetland 

(New Jersey Department of Environmental Protection, 2010). 

The basin is still under development and population has 

increased 1.17 percent from 54,733 to 55,378 between 2000 

and 2010 (U.S. Bureau of Census, 2012). Six major roads and 

one footbridge span the channel within the study reach (fig. 2).

Previous Studies

The current FIS for Ridgewood (Federal Emergency 

Management Agency, 2005) was completed by Natural 

and Technological Hazards Management Consulting, Inc. 

(NTHMC, 2004) in 2004. The study provided information on 

the 10-, 2.0-, 1.0-, and 0.2-percent annual exceedance probability water-surface profiles and associated flood plain maps 

for the Saddle River. Estimates of the peak discharges for 

these annual exceedance probability floods along the Saddle 

River, as shown in table 2 for the study reach, were described 

by FEMA (2005).
Introduction 3

ROCKLAND

NEW YORK

NEW JERSEY

P

a ss aic

R i ver

S addle

River

BERGEN

PASSAIC

ESSEX

Study area

01390450

01391000

01390500

01391500

74°15' 74°10' 74°05' 74°

41°05'

41°

40°55'

Base from U.S. Geological Survey 

1:24,000 scale digital data

EXPLANATION

Saddle River drainage 

basin boundary

U.S. Geological Survey 

streamgage and number 01390500

0 2 4 MILES

0 2 4 KILOMETERS

PENNSYLVANIA

NEW JERSEY

NEW YORK

DELAWARE

ATLANTIC OCEA

41°

40°

39°

75° 74°

Valley and Ridge

New England

Piedmont

Coastal Plain

0 20 MILES

0 20 KILOMETERS

Figure 1. Location of study reach for Saddle River and location of U.S. Geological Survey streamgages, in New Jersey.
4 Flood-Inundation Maps for the Saddle River in Ho-Ho-Kus Ridgewood, and Paramus, New Jersey, 2013

Table 1. U.S. Geological Survey streamgage information for Saddle River at Ridgewood, New Jersey.

[Station location is shown in figure 1; ft3/s, cubic feet per second; NAVD 88, North American Vertical Datum of 1988]

Station name Saddle River at Ridgewood, New Jersey

Station number 1390500

Drainage area (square miles) 21.6

Latitude 40o

59’06”

Longitude 74o

05’26”

Period of peak-flow record (water years1) 1945, 1955–2013

Maximum recorded stage, in feet, gage datum 

(and elevation, in feet above NAVD 88) and date 13.4 (84.16) on September 16, 1999

Maximum discharge, in ft3

/s, and date 6,770 on August 28, 2011

Historic peak-of-record, in ft3

/s, and date 6,800 on July 23, 1945

1

Water year is the 12-month period from October 1 of one year through September 30 of the following year and is designated by the calendar year in which 

it ends.

Table 2. 10-, 2-, 1-, and 0.2-percent annual exceedance probability peak-discharge estimates, drainage areas, and percentage of 

total discharge for selected locations on the Saddle River in New Jersey (from Federal Emergency Management Agency, 2005)

[mi2, square miles; ft3/s, cubic feet per second; NJ, New Jersey]

Location on 

Saddle River

Drainage 

area 

(mi2

)

Discharge 

estimate, 

10- percent 

exceedence 

probability 

(ft3

/s)

Discharge 

estimate, 

2- percent 

exceedence 

probability 

(ft3

/s)

Discharge 

estimate, 

1- percent 

exceedence 

probability 

(ft3

/s)

Discharge 

estimate, 

0.2- percent 

exceedence 

probability 

(ft3

/s)

Percentage 

of total 

discharge

At State Route 

17, Saddle 

River at 

Ridgewood, NJ 

streamgage

21.6 2,330 4,720 6,240 11,600 100

Upstream of 

confluence 

with Hohokus 

Brook

23.2 2,460 4,980 6,580 12,200 100
Introduction 5

01390500

17

Village of

Ridgewood

Paramus 

Borough

Ho-Ho-Kus 

Borough

Washington 

Township

Glen Rock

Borough

Village of

Ridgewood

Paramus 

Borough

Ho-Ho-Kus 

Borough

Washington 

Township

Glen Rock

Borough

G A R D E N S T A T E P A R K W A YG A R D E N S T A T E P A R K W A Y

G R O V E S T R E E T

E A S T R I D G E W O O D A V E N U E

H O L L Y W O O D A V E N U E

S

a

d

d

l

e

R i v e

r

L I N W O O D A V E N U E

B O G E R T R O A D

( F o o t b r i d g e )

H o

h

o

k

u

s

B r o

o k

S a

d d l e

B r

o

o

k

74°07' 74°06' 74°05' 74°04'

41°00'

40°59'

40°58'

0

0 0.5

0.5

1 MILE

1 KILOMETER

Base from U.S. Geological Survey 

1:24,000 scale digital data

Limit of study reach

Flow arrow—Indicates 

direction of water flow

Bridge

Model cross-section line

U.S. Geological Survey 

streamgage and number

State route marker

01390500

EXPLANATION

17

Figure 2. Location of study reach and direction of flow for the Saddle River at Ridgewood, New Jersey.
6 Flood-Inundation Maps for the Saddle River in Ho-Ho-Kus Ridgewood, and Paramus, New Jersey, 2013

Constructing Water-Surface Profiles

The water-surface profiles used to produce the 10 floodinundation maps in this study were computed by using HEC–

RAS, version 4.1.0 (U.S. Army Corps of Engineers, 2010) 

with a hydraulic model, created in 2004, provided by Natural 

and Technological Hazards Management Consulting, Inc. 

(NTHMC) for the Saddle River. HEC–RAS is a one-dimensional step-backwater model for simulation of water-surface 

profiles with steady-state (gradually varied) or unsteady-state 

flow computation options. The HEC–RAS analysis for this 

study was done by using the steady-state flow computation 

option. An unsteady-state model would be more appropriate if 

the river had dynamic streamflow conditions such as backwater or tidal flow.

Hydrologic and Steady-State Flow Data

The study reach includes one USGS streamgage 

(01390500) with a period of record from October 1954 to the 

current water year 2013 (fig. 1; table 1). Water level (stage) is 

measured continuously in real-time through a satellite radio 

transmitter, and continuous records of streamflow are computed at this site. Stage data from this streamgage are referenced to a local datum but can be converted to water-surface 

elevations referenced to the NAVD 88 by adding 70.76 ft.

Steady-state flow data consisted of flow regime, boundary conditions (either known stage associated with a discharge 

measurement, critical depth, normal depth, or a streamgage 

stage-discharge relation value), and peak discharge information. Subcritical flow regime was assumed for the simulations. 

Normal depth was used as the downstream boundary condition 

for the reach. The slope required for calculation of normal 

depth, 0.002, was computed from the average streambed slope 

through the study reach. The peak discharge data for the study 

reach were obtained from field measurements and the stagedischarge relation (rating number 23.0) that was developed by 

the USGS for streamgage 01390500.

Topographic and Bathymetric Data

Channel cross sections were developed from NTHMC 

field surveys that were conducted in 2004 (fig.2); these cross 

sections provided detailed channel-elevation data below the 

water surface and were collected by using hydroacoustic 

instrumentation to measure depth and Differential Global 

Positioning System instrumentation to determine horizontal position. Light Detection and Ranging (lidar) data were 

used to create 3-meter (9.84-ft) digital elevation data, from 

which elevations for the portions of the cross sections that 

were above the water surface at the time of the surveys were 

obtained. The lidar data were collcted during 2006–07, and 

post-processing of these data was completed by the U.S. 

National Geospatial-Intelligence Agency in 2007 (National 

Geospatial-Intelligence Agency, 2007).

Various manmade drainage structures (bridges, culverts, 

and roadway embankments) in and along the stream affect or 

have the potential to affect water-surface elevations during 

floods along the stream. To properly account for seven bridges 

(fig. 2) in the model, the structural dimensions were measured 

and surveyed in the field concurrently with the stream-channel 

surveys conducted by NTHMC. A detailed description of 

the methods used to acquire and process the topographic and 

bathymetric data can be found in Bales and others (2007).

Energy-Loss Factors

Manning’s roughness coefficients (“n” values) for energy 

(friction) loss calculations were included in the hydraulic 

model provided by NTHMC and ranged from 0.025 to 0.035 

for the main channel and 0.020 to 0.10 for the overbank areas 

modeled in this analysis. Channel conditions in the study reach 

are typified by bed material consisting of coarse gravel and 

cobbles with occasional scattered boulders and light brush on 

the banks. Overbank conditions throughout the study reach are 

variable. About 14 percent of the reach is still classified as forested, and 78 percent is classified as urban or developed (New 

Jersey Department of Environmental Protection, 2010). Dense 

vegetation and paved impervious surfaces are often present in 

the overbank within the same cross section. Roughness coefficients provided with the hydraulic model were considered 

verified by field conditions and remained unaltered.

Model Calibration and Performance

The hydraulic model was calibrated to 10 points representing the most current stage-discharge relation (rating 

number 23.0) at the USGS streamgage 01390500. Additionally, the model was calibrated to two recent measured peak 

discharges at the gage as shown in table 3. Model calibration 

is typically accomplished by adjusting Manning’s n values 

and, in some cases, changing the channel cross section or 

slope until the results of the hydraulic computations closely 

agree with the known flood discharge and stage values. It was 

unnecessary to adjust the aforementioned parameters for this 

particular hydraulic model. The simulated elevations at USGS 

streamgage 01390500 for the 12 calibration points agreed 

exactly with the target elevations. The results demonstrate that 

the model is capable of simulating accurate water levels over a 

wide range of flows in the basin.

Development of Water-Surface Profiles

Profiles were developed for a total of 10 stages at 1-ft 

intervals from 5.0 ft to 14.0 ft, gage datum (75.8 to 84.8 ft, 

NAVD 88) as referenced to USGS streamgage 01390500. 

Discharges corresponding to the various stages were obtained 

from the most current stage-discharge relation (rating number 

23.0) for the station.
Constructing Water-Surface Profiles 7

Discharges for all profiles (table 4) upstream from the 

confluence with Hohokus Brook, 3.3 mi downstream from 

station 01390500 on the Saddle River, were selected with 

the assumption that the percentage contribution to the total 

flow was the same as that assumed for the 0.1-percent annual 

exceedance probability flood from the 2005 FIS (table 2). The 

increase in flood flows at the confluence with Hohohus Brook 

is a result of runoff from the developed areas in the intervening drainage area.

Table 3. Measured peak discharges and gage heights for selected peaks at the U.S. Geological Survey streamgage Saddle River at 

Ridgewood, New Jersey (station 01390500).

[ft3/s, cubic feet per second; ft, feet]

Date of peak Peak discharge 

(ft3

/s)

Peak gage height 

(ft)

16-Sep-99 5,380 13.4

28-Aug-11 6,770 11.42

Table 4. Estimated discharges, in cubic feet per second, for corresponding stages and water-surface elevations at selected 

locations along the Saddle River, Ridgewood , New Jersey.

Location

Stage, in feet above gage datum

(elevation, in feet above NAVD 88)

Associated with the indicated discharge value, in cubic feet per second

5 6 7 8 9 10 11 12 13 14

(-75.8) (-76.8) (-77.8) (-78.8) (-79.8) (-80.8) (-81.8) (-82.8) (-83.8) (-84.8)

At State Route 17, Saddle 

River at Ridgewood, NJ 

streamgage

990 1,530 2,210 3,010 3,960 5,040 6,270 7,380 8,190 8,870

Upstream of confluence 

with Hohokus Brook 1,040 1,610 2,330 3,180 4,180 5,320 6,620 7,790 8,640 9,360

Sheet No. 1 2 3 4 5 6 7 8 9 10
8 Flood-Inundation Maps for the Saddle River in Ho-Ho-Kus Ridgewood, and Paramus, New Jersey, 2013

Inundation Mapping

Flood-inundation maps were created for the Saddle River 

at Ridgewood streamgage (station 01390500). The maps were 

created in a geographic information system by combining the 

water-surface profiles and digital elevation model data derived 

from the lidar data. The 3-meter (9.84-ft) digital elevation 

model data were derived from lidar data obtained from the 

National Geospatial-Intelligence Agency (National GeospatialIntelligence Agency, 2007).

Each digitized cross-section line used for the study area 

was attributed with a HEC-RAS calculated water-surface 

elevation for each of the 10 profiles. The flood surfaces were 

generated by using an iterative finite-difference interpolation 

technique found in the ArcGIS Topo to Raster tool. Topo to 

Raster is an interpolation method specifically designed for 

the creation of hydrologically correct digital elevation models 

(Environmental Systems Research Institute, Inc., 2012). Inputs 

into the tool include contour data derived from the digital 

cross sections that had been attributed with the NAVD 88 

water-surface elevations, in feet, from the water-surface 

profiles computed by the HEC-RAS model and boundary 

data using the study-area polygon. Depth-of-water grids were 

generated by subtracting the flood water-surface elevation of 

the study-area digital elevation model from the flood watersurface raster layer. The map products show estimated floodinundated areas overlaid on high-resolution, geo-referenced, 

aerial photographs of the study area for each of the water-surface profiles that were generated by the hydraulic model.

There is a discrepancy in the water-surface-elevation 

value from the HEC-RAS model output and the water-surfaceelevation value used to create the water-surface profile layer 

for the 13-ft stage for six cross-section lines around Route 17 

in the Village of Ridgewood. In a review of the output data 

from the hydraulic model, the water-surface-elevation values 

for the 13-ft stage layer were found to be higher than those 

from the 14-ft stage layer. Water-surface-elevation values 

were adjusted in these six cross sections to maintain hydrologic integrity. The adjusted water-surface-elevation value is 

the average of the 12-ft and 14-ft stage water-surface elevations. Values in all other cross-sections in the 13-ft stage layer 

remain unmodified.

Saddle River, New Jersey, Flood-Inundation 

Maps on the Internet

The flood-inundation maps and current study documentation are available online at the U.S. Geological Survey 

Publications Warehouse (http://dx.doi.org/10.3133/sim3299). 

Also, a Flood Inundation Mapping Science Web site has been 

established to provide a portal for USGS flood-inundation 

study information to the public at http://water.usgs.gov/

osw/flood_inundation/. The Web portal provides a link to 

interactive online map libraries that can be downloaded 

as commonly-used electronic file formats, such as pdf and 

KMZ (http://wim.usgs.gov/FIMI/FloodInundationMapper.

html). In the latter link, each stream reach displayed contains 

further links to the USGS National Water Information System (NWISWeb) graphs of the current stage and streamflow 

at the USGS Saddle River at Ridgewood streamgage (station 01390500) to which the inundation maps are referenced. 

A link also is provided to the NWS AHPS site (http:/water.

weather.gov/ahps/) at which USGS-provided stage data also 

can be viewed. The estimated flood-inundation maps are 

displayed in sufficient detail to note the extent of flooding with 

respect to individual structures so that preparations for flooding and decisions for emergency response can be performed 

efficiently. Roadways and bridges were closely reviewed and 

are shown as shaded (inundated and likely impassable) or not 

shaded (dry and passable) to facilitate emergency planning 

and use. Bridges that have a simulated water level surface at 

the low chord of the bridge deck or higher are depicted to be 

inundated (table 5). However, buildings that are shaded do not 

reflect inundation but denote that bare earth surfaces in the 

vicinity of the buildings are inundated. When the water depth 

(as indicated in the Web Mapping Application by holding the 

cursor over an inundated area) in the vicinity of the building 

of interest exceeds that building’s height, the structure can be 

considered fully submerged.

Disclaimer for Flood-Inundation Maps

The flood-inundation maps should not be used for 

navigation, regulatory, permitting, or other legal purposes. 

The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or 

responsibility resulting from the use of this information. 

Uncertainties and Limitations Regarding Use of 

Flood-Inundation Maps

Although the flood-inundation maps represent the boundaries of inundated areas with a distinct line, some uncertainty 

is associated with these maps. The flood boundaries shown 

were estimated on the basis of water stages and streamflows at 

the USGS streamgage on the Saddle River at Ridgewood, New 

Jersey (01390500). Water-surface elevations along the stream 

reaches were estimated by steady-state hydraulic modeling, 

assuming unobstructed flow, and by using streamflows and 

hydrologic conditions anticipated at the USGS streamgage. 

The hydraulic model reflects the land-cover characteristics and 

any bridge or other hydraulic structure existing as of 2013. 

Unique meteorological factors (timing and distribution of 

precipitation) may cause actual streamflows along the modeled 

reach to vary from those assumed during a flood, which may 

lead to deviations in the water-surface elevations and inundation boundaries shown. Additional areas may be flooded due 

to unanticipated conditions, such as changes in the streambed 

elevation or roughness, backwater into major tributaries along 

a main stem river, or backwater from localized debris or ice 
Summary 9

Table 5. Occurrence of bridge inundation determined from simulated water-surface profiles corresponding to stages for the Saddle 

River at Ridgewood, New Jersey streamgage (USGS streamgage 01390500).

Stage (feet) Bridge inundated

5.0 None

6.0 None

7.0 None

8.0 None

9.0 None

10.0 Linwood Avenue and State Route 17

11.0 Linwood Avenue, State Route 17, and footbridge

12.0 Grove Street, Linwood Avenue, State Route 17, and footbridge

13.0 Grove Street, Linwood Avenue, State Route 17, and footbridge

14.0 Grove Street, Linwood Avenue, State Route 17, and footbridge

jams. The accuracy of the floodwater extent portrayed on 

these maps will vary with the accuracy of the digital elevation 

model used to simulate the land surface. If this series of floodinundation maps will be used in conjunction with National 

Weather Service (NWS) river forecasts, the user should be 

aware of additional uncertainties that may be inherent or factored into NWS forecast procedures. The NWS uses forecast 

models to estimate the quantity and timing of water flowing 

through selected stream reaches in the United States. These 

forecast models (1) estimate the amount of runoff generated 

by precipitation and snowmelt, (2) simulate the movement 

of floodwater as it proceeds downstream, and (3) predict the 

flow and stage (and water-surface elevation) for the stream at 

a given location (AHPS forecast point) throughout the forecast 

period (every 6 hours and 3 to 5 days out in many locations). 

For more information on AHPS forecasts, please see: http://

water.weather.gov/ahps/pcpn_and_river_forecasting.pdf. 

Summary

A series of 10 estimated flood-inundation maps were 

developed in cooperation with the New Jersey Department of 

Environmental Protection for the Saddle River in New Jersey. 

The maps cover a 5.4-mile reach from Hollywood Avenue 

in Ho-Ho-Kus Borough downstream through the Village of 

Ridgewood and Paramus Borough to the confluence with 

Hohokus Brook in the Village of Ridgewood. These maps, 

available at a U.S. Geological Survey (USGS) Web portal, 

in conjunction with the real-time stage data from the USGS 

streamgage at Saddle River at Ridgewood, New Jersey (station 

01390500), will help to guide the general public in taking individual safety precautions and will provide municipal officials 

with a tool to efficiently manage emergency flood operations 

and flood mitigation efforts.
10 Flood-Inundation Maps for the Saddle River in Ho-Ho-Kus Ridgewood, and Paramus, New Jersey, 2013

The maps were developed by using the U.S. Army Corps 

of Engineers’ HEC–RAS program to compute water-surface 

profiles and to delineate estimated flood-inundation areas for 

selected stream stages. The maps show estimated (shaded) 

flood-inundation areas overlaid on high-resolution, geo-referenced, aerial photographs of the study area for stream stages 

between from 5.0 ft to 14.0 ft, gage datum (75.8 to 84.8 ft, 

NAVD 88) at the Saddle River at Ridgewood streamgage. 

Interactive use of the maps on the USGS Flood Inundation 

Mapper Web site can give users a general indication of depth 

of water at any point by using the mouse cursor to click within 

the shaded areas. These maps can be accessed through the 

USGS Flood Inundation Mapping Science Web site at http://

water.usgs.gov/osw/flood_inundation/.

References Cited

Bales, J.D., Wagner, C.R., Tighe, K.C., and Terziotti, Silvia, 2007, Lidar-derived flood-inundation maps for realtime flood-mapping applications, Tar River Basin, North 

Carolina: U.S. Geological Survey Scientific Investigations 

Report 2007–5032, 42 p.

Environmental Systems Research Institute, Inc., 2010, Products—ArcGIS, accessed May 16, 2011, at http://www.esri.

com/products/index.html.

Environmental Systems Research Institute, Inc., 2012, 

Using the Topo to Raster Tool, accessed April 3, 2014, 

at http://webhelp.esri.com/arcgisdesktop/9.3/index.

cfm?TopicName=Using%20the%20Topo%20to%20

Raster%20tool .

Federal Emergency Management Agency (FEMA), 2005, 

Flood Insurance Study, Bergen County, New Jersey: Washington, D.C., September 30, 2005, 4 p.

National Geospatial-Intelligence Agency, 2007, LiDAR-Metro 

N. Jersey 2006–07: Springfield, Virginia.

National Weather Service, 2013, National Weather Service 

Glossary, accessed September 12, 2013 at http://w1.weather.

gov/glossary/index.php?word=action+stage. 

Natural and Technological Hazards Management Consulting, Inc. (NTHMC), 2004, Final hydrology: Riverine flood 

insurance studies in FEMA Region II New Jersey FY-01, 

Saddle River, New Jersey: Montvale, N.J., NTHMC. 107 p.

New Jersey Department of Environmental Protection, 2010, 

NJDEP 2007 Landuse/Landcover Update, State of New 

Jersey: Trenton, N.J.

U.S. Army Corps of Engineers, Hydrologic Engineering 

Center, 2010, HEC–RAS River Analysis System, Hydraulic Reference Manual, version 4.1: Davis, CA, [variously 

paged].

U.S. Bureau of Census, 2012, Census 2010 State and county 

quick facts, accessed September 12, 2013, at http://quickfacts.census.gov/qfd/states/34000.html.
Prepared by the West Trenton Publishing Service Center

For more information, contact:

New Jersey Water Science Center

U.S. Geological Survey

3450 Princeton Pike, Suite 110

Lawrenceville, NJ 08648

http://nj.usgs.gov/
Watson and Niemoczynski—Flood-Inundation Maps for the Saddle River in Ho-Ho-Kus Ridgewood, and Paramus, New Jersey, 2013—Scientific Investigations Map 3299

ISSN 2329–132X (online) 

http://dx.doi.org/10.3133/sim3299