Honghai Qi, PhD, PE.Lawrenceville, New Jersey

Optimal Sluice Gate Operations for Flood Mitigation Study - City of Rye, New York

Outline

Project Background

Introduction to Blind Brook Watershed

Analysis of Recent Storm Event (April 30 to May 1, 2014)

Improvement to Sluice Gate Operations

Conclusions and Recommendations

Project Background

The City of Rye, NY has experienced significant property damage due to flooding along Blind Brook.

Several studies have been conducted to analyze the flooding.

Studies recommended steps to reduce/ mitigate flooding caused by Blind Brook.

Blind Brook Watershed Blind Brook, a tributary to the

Long Island Sound, has a drainage area of 10.9 mi2.

Drainage area includes City of Rye, Village of Rye Brook, Town/Village of Harrison, Village of Port Chester, and City of White Plains.

The length of the Blind Brook watershed is approximately 9 miles; width varies from 0.5 miles to 2 miles.

96.7% of total drainage area is in New York, and 3.3% of total area in Fairfield County, Connecticut .

Land Use and Soil Data

FEMA Study Effective FEMA

Study dated September 27, 2007

Community-Panel Numbers 36119C0356F and 36119C0352F

No Preliminary FEMA Maps issued since Hurricane Sandy (2012)

Rainfall Map

Average Annual Rainfall Depth 47 inches

24-Hour Duration, Type III Rainfall

Normal Soil Antecedent Moisture Content

ReturnPeriod

Rainfall Depth

(inches)

2-Year 3.5

5-Year 4.3

10-Year 5.0

25-Year 5.7

50-Year 6.4

100-Year 7.2

Previous Studies

November 2001, City of Rye – Flood Mitigation Plan identified Bowman Avenue Dam site for possible flood control

March 2008, SELLS issued Flood Mitigation Study that identified feasible alternatives including:

Orifice optimization (Sluice Gate Project)

Maximizing storage potential at Upper Pond

Refine costs and determine downstream benefit / upstream impacts

April 2012, SELLS was tasked with Upper Pond Study

Soiltesting Inc. (rock probes and borings)

WSP Energy and Environmental (contamination study)

RIZZO Associates (Hydrology and Hydraulics)

Location of Upper Pond / Dam

The Upper Pond / Bowman Avenue Dam is located within the Village of Rye Brook immediately upstream of I-287.

Originally constructed in the 1900's, the dam and the Upper Pond were used for ice production. In 1941, the dam collapsed and was rebuilt.

Current capacity of the Upper Pond is 145 ac-ft.

Bowman Avenue Dam

Reinforced-concrete gravity dam, 119 ft long and 13 ft high.

Based on aerial photos from 1925 and 2013, the dam site has changed considerably.

Only 25% of Upper Pond is available for flood storage.

Source: USGS. Image date: April, 2013

Sluice Gate on Bowman Avenue Dam

Left: Original Right: Present - Dam has a 15-ft wide by 11.5-ft high outlet at the bottom of the dam, and a 20-ft wide by 2-ft high spillway at the top. - Operation of sluice gate is based on Sell’s rule developed in 2008.

Recent Storm Event (04/30-05/01, 2014)

Advanced Hydrologic Prediction Service (AHPS) via National Weather Service (NWS) has gridded daily rainfall data for the Blind Brook Watershed.

The rainfall depth was approximately equivalent to a 2-year event.

RainfallGage

RainfallApril 30(inches)

RainfallMay 1

(inches)

TotalRainfall(inches)

No. 1 0.399 3.30 3.70

No. 2 0.40 3.70 4.10

Runoff from Recent EventPeak Discharges from Subwatershed

HEC-RAS Flow Change Input

Locations for Comparing Downstream Flooding

Sluice Gate Opening

WSE Measured at the Gauge inside Upper Pond.

Two Openings of the Sluice Gate

Flow During Sluice Gate Opening

Two Man-Made Peak Discharges

W.S. Elev. for “No Operations” vs Sluice Gate Opening

Locations HEC-RAS

Cross Section

No Gate Operations

Results

(ft)

Sluice Gate

Open Results

(ft)

Difference

(ft)

D/S I-287 XS 2230.179 33.09 34.38 +1.29

Purchase

Street XS 1508.033 27.38 28.46 +1.08

Mendota

Avenue XS 733.8118 24.08 24.83 +0.75

Highland

Road XS 677.1604 23.51 24.33 +0.82

U/S I-95 XS 504.3617 22.69 23.27 +0.58

* Predicted results represent water surface elevation resulting from sluice gate operating with current programming.

*

Current Gate Operation Based on Sells’ Study

For each storm event, the sluice gate should be opened to the corresponding optimal height for that event, in order to achieve the maximum water surface elevations at various downstream locations.

Since this event was equivalent to a 2-year event, the gate should remain close during the event based on rule above.

However, the current programming of the gate resulted in fully opening of the gate to its maximum possible height of 7.3 ft.

Gate Operation Based on Gauge at Indian Village

Q2 = 848 cfs Q5 = 1,844 cfs

Q10 = 2,622 cfsQ25 = 3,140 cfs

Q50 = 3,672 cfsQ100 = 4,354 cfs

E = 0.0000003551Q2 + 0.0001460990Q + 23.0709263024R² = 0.9704077109

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Wate

r S

urf

ace E

levati

on

s a

t X

S 8

90.5

97

to C

lose G

ate

#2

(E -

ft)

Peak Discharges at XS 890.597 (Q - cfs)

Gate Operation Based on Gauge at Downstream I-287

Q2 = 777cfsQ5 = 1,813 cfs

Q10 = 2,636 cfs Q25 = 3,255 cfs Q50 = 3,931 cfs Q100 = 4,790 cfs

E = -0.0000002041Q2 + 0.0022258388Q + 30.0516609098R² = 0.9961578546

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Wate

r S

urf

ace E

levati

on

s a

t X

S 2

230.1

79

to C

lose S

luic

e G

ate

(E -

ft)

Peak Discharges at XS 2230.179 (Q - cfs)

Compared with the previous scenario, this scenario has the gauge located 170 ft downstream of I-287, and 5,800 ft upstream of I-95.

The advantage of this gauge location is to protect a larger flood-prone residential areas, and provide greater water surface elevation reductions downstream of dam.

Comparison of W.S. Elevation Reduction

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0.1 0.1 0.1 0.1 0.1

0.2

0.4 0.4

0.5 0.5

0.2 0.2

0.4

0.5 0.5

0.01 0.01 0.01 0 00.04 0.05 0.05 0.06 0.05

0.21

0.340.31 0.31

0.43

0.29

0.51

0.6 0.61

0.77

0.47

0.86

1.48 1.48

1.57

0.18

0.53

0.73 0.730.78

0 0 0 0 0

0.14

0.310.25 0.27

0.23

0.44

0.85

0.61 0.62

0.83

0.46

0.87

0.8 0.8

1.03

0.52

0.97

1.37 1.37

1.45

0.22

0.43

0.66 0.670.7

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

D/S

I-2

87

Purc

hase S

t

Mendota

Avenue

Hig

hla

nd R

oad

U/S

I-9

5

D/S

I-2

87

Purc

hase S

t

Mendota

Avenue

Hig

hla

nd R

oad

U/S

I-9

5

D/S

I-2

87

Purc

hase S

t

Mendota

Avenue

Hig

hla

nd R

oad

U/S

I-9

5

D/S

I-2

87

Purc

hase S

t

Mendota

Avenue

Hig

hla

nd R

oad

U/S

I-9

5

D/S

I-2

87

Purc

hase S

t

Mendota

Avenue

Hig

hla

nd R

oad

U/S

I-9

5

D/S

I-2

87

Purc

hase S

t

Mendota

Avenue

Hig

hla

nd R

oad

U/S

I-9

5

2-year 5-year 10-year 25-year 50-year 100-year

Wate

r S

urf

ace E

levation R

eductions

at D

ow

nstr

eam

Locations (

ft)

Sluice Gate Operation (RIZZO)

Sluice Gate Operation Based on W.S. Elevation at Indian Village

Sluice Gate Operation Based on W.S. Elevation at D/S I-287

Gate control based on I-287 gauge provides better results than Indian Village gauge.

Wat

er S

urf

ace

Elev

atio

n R

edu

ctio

ns

at

Do

wn

stre

am L

oca

tio

ns

(ft)

Resize Upper Pond

Proposed Upper Pond will a storage volume of 210 ac-ft.

Contour Map of Resizing Upper Pond

Area Volume

(acre) (acre-ft)

41 5.89 0.00

42 8.00 6.91

43 9.81 15.80

44 10.76 26.09

45 11.18 37.05

46 11.50 48.40

47 11.88 60.08

48 12.28 72.16

49 12.62 84.61

50 12.89 97.37

51 13.13 110.38

52 13.42 123.66

53 13.68 137.21

54 13.97 151.03

55 14.26 165.15

56 14.58 179.57

57 14.94 194.33

58 15.50 209.54

Elevation

Cumulative Effect 1: Resize Upper Pond and Gate Operations at Downstream of I-287

0.14 0.14 0.13 0.13 0.1

0.61

1.05

0.8 0.82

1.07

0.68

1.17

1.7 1.711.81

0.55

0.96

1.36 1.361.45

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

D/S

I-2

87

Pu

rch

ase

St

Men

do

ta A

ven

ue

Hig

hla

nd

Ro

ad

U/S

I-9

5

D/S

I-2

87

Pu

rch

ase

St

Men

do

ta A

ven

ue

Hig

hla

nd

Ro

ad

U/S

I-9

5

D/S

I-2

87

Pu

rch

ase

St

Men

do

ta A

ven

ue

Hig

hla

nd

Ro

ad

U/S

I-9

5

D/S

I-2

87

Pu

rch

ase

St

Men

do

ta A

ven

ue

Hig

hla

nd

Ro

ad

U/S

I-9

5

2-year 10-year 50-year 100-year

Wat

er S

urf

ace

Ele

vati

on

Red

uct

ion

s(f

t)

Downstream water surface elevation reduction ranges from 0.1 ft ~ 1.81 ft.

Additional Detention Areas

Westchester County Airport: 2 detention ponds by expanding existing stormwater management ponds

SUNY-Purchase: 2 detention areas

PepsiCo: 1 detention area

Hutchinson River Parkway: 3 detention areas

Subwatershed SW2: 2 detention ponds by expanding existing stormwater management ponds.

Cumulative Effect 2: SUNY-Ponds, Resize Upper Pond and Gate Operations at Downstream of I-287

0.19 0.19 0.18 0.18 0.13

0.78

1.25

1.01 1.04

1.32

0.99

1.64

2.34 2.35

2.58

0.87

1.54

2.37 2.392.54

0

0.5

1

1.5

2

2.5

3

D/S

I-2

87

Pu

rch

ase

St

Men

do

ta A

ven

ue

Hig

hla

nd

Ro

ad

U/S

I-9

5

D/S

I-2

87

Pu

rch

ase

St

Men

do

ta A

ven

ue

Hig

hla

nd

Ro

ad

U/S

I-9

5

D/S

I-2

87

Pu

rch

ase

St

Men

do

ta A

ven

ue

Hig

hla

nd

Ro

ad

U/S

I-9

5

D/S

I-2

87

Pu

rch

ase

St

Men

do

ta A

ven

ue

Hig

hla

nd

Ro

ad

U/S

I-9

5

2-year 10-year 50-year 100-year

Wat

er S

urf

ace

Ele

vati

on

Red

uct

ion

s (f

t)

Downstream water surface elevation reduction ranges from 0.13 ft ~ 2.58 ft.

Conclusions

Recent storm event and the actual gate movement were modeled, and the effect on downstream flooding was evaluated.

Two new locations were investigated for the gauge to control the sluice gate. The location of the gauge would be moved to a point downstream of the dam, and upstream of the flood-prone areas of Indian Village and downstream of I-287.

Future work includes install more gauges along the stream, so that the model can be calibrated more precisely with measured water surface elevations to better represent Blind Brook.

Thank you!

Questions and Comments?

City of Rye, New York1051 Boston Post RoadRye, New York 10580Phone: (914) 967-5400

2000 Lenox Drive, 3rd FloorLawrenceville, New Jersey 08648Phone: (609) 512-3500Fax: (609) 512-3600