Understanding Flooding on the Pompton River

Major FloodsMay 1968

April 1984

March 2010

“Minor” Floods

March 21, 2003

Harrison Road

Pompton River atJackson Ave

Many Floods

River FloodingSevere Flooding in Pequannock Township

results from River Flooding on the Pequannock and Pompton Rivers:The volume of water coming from upstream

exceeds the capacity of the river which then overflows into surrounding area’s and / or

The volume of water entering the Pompton River exceeds the volume that flows out at the Passaic River, causing water in the Pompton to get “backed up” filling the river basin.

Local DrainageRainfall in the Western section of the

Township flows South through the East & West ditches to Beaver Brook in Lincoln Park, then to the Pompton River.

Rainfall in the Eastern section of the Township flows East directly to the Pompton River through small local streams and brooks.

These same Streams carry flood waters from a rising Pompton River back into the neighborhoods they drain.

Flood Gates provide protection from a rising river until the water level overtops Route 23.

Changes in Flood EvolutionEvery Flood event evolves differentlyFlood Evolution is impacted by:

River Height at the start of a StormLength & Intensity of RainGroundwater Level & Ground Saturation

The effect of Route 23Homes flooded in 1968

(River Height 22.18’) had no water in 2010 (22.78’)

Homes with over 2 feet of water in 1984 (River Height 24.47’) had no water in 2010

The Reconstruction of Route 23 was completed in 1986–87 which raised the road surface and added a concrete median.

The Pompton RiverForms at the convergence of three rivers at the

Northeast corner of Pequannock Township.The Pequannock RiverThe Wanaque RiverThe Ramapo River

Drains an area of 355 square miles in Northern New Jersey and Southeastern New York Sate.

One inch of rain over the basin produces 6,169,025,280 Gallons, or 824,736,000 Cubic Feet of water.

Base River Elevation – 160’ at Jackson Avenue

A small river drains a large area Historical Crests for Pompton River at Pompton Plains

(1) 24.47 ft on 04/06/1984(2) 22.78 ft on 03/14/2010(3) 22.18 ft on 05/30/1968(4) 21.72 ft on 04/16/2007(5) 21.00 ft on 09/17/1999(6) 20.42 ft on 04/03/2005(7) 20.37 ft on 02/03/1973(8) 19.56 ft on 04/10/1980(9) 18.65 ft on 11/09/1977(10) 17.86 ft on 10/09/2005(11) 17.56 ft on 10/13/2005(12) 16.96 ft on 01/28/1996(13) 16.90 ft on 03/31/2010(14) 16.78 ft on 12/12/2003(15) 16.32 ft on 05/12/1998(16) 14.86 ft on 10/21/1996(17) 14.86 ft on 12/02/1996

The Pequannock RiverFlooding impacts Harrison Road section

Floods more frequently than other area’s of Township

Drains from Hamburg Mountain SoutheastAt the point of the Macopin Dam (along Rt.

23) it drains 63.7 square milesThere are Four (4) Reservoirs along the

Pequannock which are part of the City of Newark Water Supply

Elevation – 549 feet at Macopin Dam

The Wanaque RiverAt the gauge just downstream from the

Raymond Dam, the river drains an area of 90.4 square miles

A minimal base flow of approximately 20 cubic feet per second (cfs) unless the Wanaque Reservoir is full

There are two Reservoirs on the river owned by the North Jersey District Water Supply Commission (NJDWSC)

Elevation – 210 feet at Wanaque Avenue

The Ramapo RiverAt Dawes Highway, the Ramapo River drains

an area of 160 square milesThere are no true reservoirs on the Ramapo

RiverDiversion from Pompton Lake can be used to

fill the Wanaque and Oradell Reservoirs (Capacity = 300,000,000 Gallons)

Elevation – 175 feet at Dawes Highway; 253 feet at Route 17 (Mahwah)

The Passaic RiverAt Two Bridges, the Passaic River drains an

area of 734 square milesBase River Elevation – 155 feet at the mouth

of the Pompton RiverThe Passaic River at Two Bridges rises

slower and crests later than the PomptonHigh water levels on the Passaic can slow the

drainage of the Pompton, causing it to back up into low lying area’s

Aggravating & Mitigating FactorsRiver System Capacity

Shallow Slope / SedimentationReservoir CapacityGround Conditions

Saturation / Ground Water / FrozenSnowFoliagePrecipitation Rate

River CapacityRiver systems are capable of handling

significant increases in flow before they floodThe median flow of the Pompton River at

Jackson Avenue is 345 cfs, or 222 Million Gallons per Day

The approximate flow at Flood stage is 8,000 cfs, or 5.15 Billion Gallons per Day

The lower the river flow at the start of a rain event, the more capacity there is to handle flow without flooding.

Reservoir CapacityTotal Capacity of the Wanaque Reservoir is 29.6

Billion GallonsAs long as the Wanaque Reservoir is below capacity

there is effectively no flow into the Pompton from the Wanaque, decreasing the drainage area by ¼ (90 sq mi)

At 75% of capacity, the Wanaque Reservoir can absorb 4.7” of rain without adding flow to the Pompton

Newark’s Reservoirs on the Pequannock River have a combined capacity of 14.4 Billion Gallons.

Forecasting FloodingWeather ReportsNWS Watches & WarningsNWS River Forecasts

Advanced Hydrologic Prediction ServiceMonitoring Conditions

RainfallRiver LevelsReservoir Levels

Watching the River

River Level PredictionsUsing Information from:

Actual Rainfall Totals & Rainfall PredictionsReview NWS – AHPS River ForecastsWatch Upstream Rivers

Total Flow & Rate of RiseWatch Upstream Reservoirs

Predict when Reservoirs will reach CapaictyWatch Pompton Lake

Predict Gate ActivationManually watch all local Stream & River

Levels

Predicting ImpactsHow High will the Water Get?

Use of Forecasting Tools & ExperienceWhat will the impacts be?

Closed Roads & AccessFlooded StreetsFlooded Homes & Businesses

When will Streets be impassable?When will Businesses be Impacted?When will Homes be subjected to Interior

Flooding?

Management DecisionsTiming vs AccuracyNotification vs EvacuationTime of Day Impacts – Who is Home?

Work Day / WeekendSchool DayLate Night

Flood Precautions for Businesses / Homeowners in light of Evacuation

Getting Information OutTownship WebsiteCable Channel 77Flood Information Phone (Recreation Line)Reverse 9-1-1Door to Door Notifications

Under Consideration:AM Radio Broadcast ChannelInstant Alert – Subscriber based Text, E-mail or

Phone

Flood Response

Agency RolesPolice – Maintain Response Capability

Increased Demand on Communications CenterTraffic, Detours & Road ClosuresSecurity for Closed Businesses &

NeighborhoodsFire – Maintain Response Capability

Notifications, Evacuations, EMS Support, Water Rescue

EMS – Maintain Response CapabilitySupport for Fire Operations, Shelter Support

Agency RolesDPW

Check & Clear Drains, Waterways & Flood GatesMaintain Operation of Water & Sewer

InfrastructureBarricades for Road Closures & DetoursStorm Debris removal from Streets

Health DepartmentHuman & Animal Shelter Operations

RecreationCoordination of Community Volunteer Efforts

Agency RolesEngineering

Evaluate Impact / Stability of Municipal Infrastructure

Prepare Damage AssessmentsConstruction Code Office

Evaluate Damaged BuildingsAssist Residents in Permitting / Repair Efforts

Office of Emergency ManagementThe Office of Emergency Management (OEM)

coordinates activities of all local agencies and obtains resources needed by response crews.

In support of this mission, OEM may:Activate the Emergency Operations Center (EOC)Declare a Local State of EmergencyCall on Specific Resources to assist Local Agencies

Maintains contact with County & State Emergency Officials to keep abreast of Regional Conditions & request additional resources, if needed.

Receding Water Clear Debris and Open RoadwaysAccess Control to Flooded NeighborhoodsEnsure Safety of Flooded HomesDistribute Clean up KitsCoordinate Community Volunteers

Food; Clean-up; DonationsCoordinate with County & State OEM; FEMADocumentation of Damage, Costs & Activities

RecoveryDebris Pick-up, Removal & DisposalRepair of Municipal Facilities &

InfrastructureContact with every affected Business &

HomeownerSafety Inspections for Businesses

Health, Fire & Construction where requiredConstruction Code Inspections for Home

Repairs

Flood InsuranceNot covered by Homeowner’sSponsored & Underwritten by NFIP (FEMA)Required by Mortgage for Properties in Flood

PlainStructure Coverage / Contents CoverageDiscounts through Community Rating System

(CRS)Repetitive Loss / Severe Repetitive Loss

Pompton Lake FloodgatesNo downstream notification of operationsDisrupts Local Flood Elevation ForecastingCan quickly inundate areas thought to be

safeDisrupt Evacuation EffortsComplicate Rescue Operations