Near-Real Time and Time-Critical Scour Monitoring at the IRIB

Objectives:

1) Investigate hydrodynamic tidal forcing in the inlet that plays a role in scour hole development

2) Monitor orientation of the bridge piers3) Monitor riprap and scour hole edge in near-real time4) Collect higher temporal resolution bathymetry

1994 1996

19992004

IRIB SCOUR PROBLEM

Images courtesy of Jeff Gebert, USACE

Over the last 12 years, scour hole depths and spatial extent have increased dramatically

Will scour holes begin to undermine protective riprap and interfere with pier stability?

IRIB PIER ORIENTATION MONITORING

Use a dual axis tilt sensor to monitor long-term pier orientation

Most appropriate pier due to potential for scour hole interference

IRIB PIER ORIENTATION MONITORING

Cabling

•One 8-conductor cable spans two piers

•This cable transmits data and powers sensor

•Limits electrical access needs to land

Powering and data collection

Waterproof Enclosure Power unit

Dataq DI-710 stand alone logger

D-Link Pocket Router

Omega Power Converter (sends power to sensor)

•Box secured to top of land-based concrete pier

•Logger and router plug into box power unit

•Sensor receives power from converter

•Will need power access from land only!

Router connects to ethernet port on logger so data can be downloaded without opening box

IRIB PIER ORIENTATION MONITORING

IRIB TIDAL CURRENT MONITORING

Use boat mounted acoustic Doppler Current Profiler to collect data over a tidal cycle.

TIMELINE

January, 2006

Install tilt sensor on bridge pier

Spring, 2007 Collect ADCP current meter data over a tidal cycle

Summer, 2007

Analyze tilt and current meter data to investigate variability

Spring, 2007

Install rotary sonar and ADCP to monitor stability of pier riprap armoring, inlet bottom, scour hole edge and to measure tidal currents

Spring, 2007

Begin high temporal resolution bathymetry collection using GPS and echo-sounder equipped wave runner

Summer, 2007

Initiate physical model study of scour hole development using current meter data for scaling

DETAILED MONITORING EFFORTS PENDING FUNDING

Do we want to include physical model study? Might be difficult for a student to complete in allotted time? However, would be a nice complement to study

WHY CONDUCT A THOROUGH INVESTIGATION?

Can answer questions such as:

1) What is the spatial and temporal variability of the scour hole?

2) What is the spatial and temporal variability of the riprap protecting the pier?

3) How are variations in riprap armament and scour hole morphology related to tidal forcing conditions?

4) How does the scour hole respond to storm events?

5) Is the rate of scour hole development increasing or decreasing?

To answer these important questions, it is necessary to collect the response AND the forcing conditions simultaneously.

3D PROFILING SONAR

Advantage: System does not need to be engineered in-house. Can be cabled to logger for near-real time internet access.

3D XYZ elevation data

Bridge mounting: Top view

Pier

East pier of North pier pair

3D PROFILING SONAR

Scanned area below sensor

sensor

Pier

Routinely image (X,Y,Z coordinates) the area directly below and adjacent to the pier

~120 ft

3D PROFILING SONAR LAYOUT

pier

Electronics Package

PierOnland

Edge of inlet

Comms cable attached to bridge deck

PC, logger

Network connected PC at Coast Guard Station

sensor

Power

Wireless connection

TIDAL CURRENT MEASUREMENT

Tidal currents must play a role in scour hole evolution and migration

Use Acoustic Doppler Current Profiler (ADCP) to obtain the time dependent tidal flow.

Communications layout is the same as the sonar

TIDAL CURRENT PROFILING

Show some example image of tidal or wave ADCP data if we can get it.

pierpier

Edge of inlet

Edge of inlet Measure current velocity

Pretty lame schematic and probably not needed

SCOUR HOLE AND RIPRAP BATHYMETRIC MAPPING

Arm

y C

orps

, 20

04

• Army corps data collected roughly every 2-3 years• Shows that the scour holes have deepened and migrated, particularly seaward holes• No indication as to the high frequency evolution of holes (tidal, storm, seasonal)• Requires more frequent and targeted monitoring

BATHYMETRIC MAPPING USING A WAVERUNNER

Will survey roughly monthly, but also some targeted surveying pre- and post-storm and surrounding a tidal cycle

BATHYMETRIC MAPPING USING A WAVERUNNER

•Example wave runner bathymetric data from the surf zone.

•Lack of waves in the inlet may simplify data collection

•Will be able to quantify scour hole variability

ITEM YEAR1 (Cost in $k)

YEAR2(Cost in $k)

3D Profiling Sonar 60 0

Computers (1 for student, 1 for data acquisition, 1 for received telemetry)

10 0

ADCP (including cables) (can we collect via other computer (how long of a cable can we use?)

35 0

Wave runner with GPS 65 0

Miscellaneous (cables, mounts, power wireless connection, NEMA enclosures)

10 2

Life vests, wet suits, wave runner upkeep 1 1

COSTS

ITEM YEAR1 (Cost in $k)

YEAR2 (Cost in $k)

Student Salary (could be less depending on start date, since Jesse presently funded)

20 20

PI Salary (Puleo; 1.5 mo, 1.5mo, Macmahan; 1.5mo, 1.5mo, Righman?)

30 30

Tech Salary 5

Travel 2.5 2.5

Fringe 12 10

Overhead 42.5 35

Total 293 100.5

COSTS Continued

This is HUGE, but necessary to get work done. They may decide they are only interested in certain aspects or not at all

BUDGET DESCRIPTION

•Large initial investment in the first year to acquire instrumentation

•Expenses in year 2 are significantly reduced and cover the salary for PI’s and the student to continue the monitoring effort and data analysis.

•In situ equipment has a lifespan of at least 5 years and can be extended if cleaned and serviced regularly

•Waverunner lifespan is roughly 10 years with adequate upkeep

•Lifespan of instruments means they can be in service until the new IRIB is completed. Monitoring can continue after old bridge is removed

•Monitoring can be modified to occur at other locations of interest to DelDot (e.g. C&D Canal Bridge) as necessary.