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“Avenues” Basin
“Scituate Ave” Basin
Staff Gauge
Staff Gauge
Seawall at Scituate Massachusetts
Test site for this project
Avenues Basin Looking Southeast
Avenues Basin Looking Northeast
Seawall
Time Stamp = 27th/0754 EST Water Level = 15.476 feet
Seawall Seawall
Stop Sign 7th & Ocean Side Dr.
Avenues Basin Flooded from Overtopping
January 27, 2015
Overwash Water Ponding in Basin
landward of Seawall
Astronomical
Tide
7th Avenue Staff Gauge
Flooding is only result of overtopping
Max level on Staff Gauge Seawall Crest 21.5 MLLW
Max Storm Tide Level 13.1 ft MLLW
Flood Water is above maximum storm tide level
Overtopping Parameterization J.P. de Waal and J.W. van der Meer
Off shore wave steepness
Dimensionless Freeboard for slopes
Adjusted Dimensionless Freeboard for slopes (Bruce)
Plunging wave dimensionless discharge
Mean overtopping discharge m³/s per meter of structure length
Data Logger
Avenues Basin Staff Gauge
& Data Logger
Data logger records water depth every 6 minutes
and is deployed prior to the storm event.
Reduction Factors
= Reduction factor for Berm/Sandbar
= Reduction factor for shallow water
= Reduction factor for foreshore roughness
= Reduction factor for angle of wave attack
Seawall Crest
Still Water Level (SWL)
Seawall toe
Algorithm Parameters Freeboard & Slope
Freeboard
Slope measured from the +2.0 MLLW level
to the seawall toe
Shallow water reduction factor J.P. de Waal & J.W. van der Meer
Larger waves break in deeper water
Smaller waves break closer to the seawall
Waves will be reduced as they shoal over a sandbar
Reduction factor for a Berm or Sandbar
J.P. de Waal & J.W. van der Meer
Reduction factor for roughness J.P. de Waal & J.W. van der Meer
Surface Type: ! Smooth Slope = 1.00 ! Grass = 0.90 to 1.00 ! Rock (1 layer) = 0.55 to 0.60 ! Rock (two or more layers) = 0.50 to 0.55
Wave Direction
Seawall
Short crested waves
Long crested waves
Angle of wave attack reduction factor
J.P. de Waal & J.W. van der Meer
046⁰
Wave Direction 075⁰
075⁰ 095⁰
GIS ArcMap 10 used to determine basin Volume
1. Create a Tin surface 2. Activate 3D Analyst 3. Cut out basin using Tin
Editing Tool 4. Use Surface Volume Tool to
compute the basin volume 5. As an alternative the polygon
volume tool can be used
2
4
3
1
5
8 ft
9 ft
8 ft
11 ft
Manhole Catch basin
18 inch R.C.P. Pipe
Drainage System
Outlet 36 inch A.C.C.M.P. Pipe
Manning Equation
" Q = quantity of flow ft³ per second " n = manning coefficient for roughness " A = cross sectional area of pipe " R = Hydraulic radius " S = Hydraulic slope
Catch Basins
Grate is partially blocked by ice, snow and debris
Grate Flow
Tidal response
No tidal response to drainage rate with constant 43.6 m³/min
rate for 30+ hours
Slope = 0.134
Slope = 0.142
Slope = 0.132
Slope = 0.131
Slope = 0.090
Seawall Divided into Sectors based on survey of slope
Surface Chart January 27, 2015 2100Z
Test Event January 27, 2015
Surface Chart November 2, 2014 1500Z
Test Event November 1, 2014
Surface Chart December 9, 2014 1800Z
Test Event December 9, 2014
Questions ??
