City of Alexandria, Virginia

KING, STRAND, AND UNION STREETS

Park & Recreation Commission

NOVEMBER 15, 2012

Daily High Tides for 2005-2011

2

Daily High Tides for 2012

3

-1

0

1

2

3

4

5

21-Jan

24-Jan

27-Jan

30-Jan

2-Feb

5-Feb

8-Feb

11-Feb

14-Feb

17-Feb

20-Feb

23-Feb

26-Feb

29-Feb

3-M

ar

6-M

ar

9-M

ar

12-M

ar

15-M

ar

18-M

ar

21-M

ar

24-M

ar

27-M

ar

30-M

ar

2-Apr

5-Apr

8-Apr

11-Apr

14-Apr

17-Apr

20-Apr

23-Apr

26-Apr

29-Apr

2-M

ay

5-M

ay

8-M

ay

11-M

ay

14-M

ay

17-M

ay

20-M

ay

23-M

ay

26-M

ay

29-M

ay

1-Jun

4-Jun

7-Jun

10-Jun

13-Jun

16-Jun

19-Jun

22-Jun

25-Jun

28-Jun

1-Jul

4-Jul

7-Jul

10-Jul

13-Jul

16-Jul

19-Jul

22-Jul

25-Jul

28-Jul

31-Jul

3-Aug

6-Aug

9-Aug

12-Aug

15-Aug

18-Aug

21-Aug

24-Aug

27-Aug

30-Aug

2-Sep

5-Sep

8-Sep

11-Sep

14-Sep

17-Sep

20-Sep

23-Sep

26-Sep

29-Sep

2-Oct

5-Oct

8-Oct

11-Oct

14-Oct

17-Oct

20-Oct

23-Oct

26-Oct

29-Oct

1-Nov

4-Nov

7-Nov

Daily High-High Tide Elevations (NAVD88)Jan 21 thru Nov 7, 2012

DATE/TIME

Max of ELEV

What causes the flooding?

• Some flooding is caused by

rainfall

- However -

• Most of the flooding is caused

by tidal backups through the

storm sewers on Strand, King

and Union Streets

4

5

• Substantially reduce

nuisance flooding

raising the elevation of

storm inlets

• Minimize impacts to

private properties

• Minimize cost

June 6th , 2012 @ 10:00 am

• The existing lowest point is along Strand Street at Elevation 1.45’

• Low points along King Street between Elevation 2.6’ and 2.8’

6

• Potomac River water surface elevations

• Elevations of existing building entrances

• Minimum slopes required for drainage

• Road and sidewalk design standards

• ADA compliance

• Cost

7

• Relocates the low point from Strand Street to King Street

• Raises lowest storm inlet opening from 1.45’ to 2.66’ (Alt.1) or 3.22’ (Alt.2)

• Annual projected flood days will be reduced from 303 to 61 (Alt.1) or 13 (Alt.2)

• Impacts to properties:

• Mai Thai (remove internal ramp) (Alt.2 only)

• Stairwell (possibly reconstruct stairs and entrance) (Alt.2 only)

• Re-Grade Portion of Boat Club Parking Lot

• Cost estimate: $925,000, (Alt.1) or $1,150,000 (Alt.2)

8

9

10

11

12

13

Flooding on the Strand

14

15

16

Depth of Flood Events

17

Approximate Annual Average Flood Depths

For Existing Roadway Elevations

Depth

Greater

Than

Strand Street

(Elev. 1.45)

King Street

(Elev. 2.43)

King & Union Street

(Elev. 3.22)

6" 223 30 7

1' 100 7 2

1.5' 30 2 <1

2.0' 7 <1 <1

2.5' 2 <1 <1

• With Alternative 1:

• Average of less than 1 incident of flooding per year at Strand Street

• Flood incidents on King Street will be shallower by 3”

• With Alternative 2:

• Average of less than 1 incident of flooding per year at Strand Street

and King Street