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 piers 3)Monitor riprap and scour hole edge in near-real time 4)Collect higher temporal resolution bathymetry

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, 2007Collect 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 Pier On land 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. pier Edge of inlet Measure current velocity Pretty lame schematic and probably not needed

SCOUR HOLE AND RIPRAP BATHYMETRIC MAPPING Army Corps, 2004 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

ITEMYEAR1 (Cost in $k) YEAR2(Cost in $k) 3D Profiling Sonar600 Computers (1 for student, 1 for data acquisition, 1 for received telemetry) 100 ADCP (including cables) (can we collect via other computer (how long of a cable can we use?) 350 Wave runner with GPS650 Miscellaneous (cables, mounts, power wireless connection, NEMA enclosures) 102 Life vests, wet suits, wave runner upkeep11 COSTS

ITEMYEAR1 (Cost in $k) YEAR2 (Cost in $k) Student Salary (could be less depending on start date, since Jesse presently funded) 20 PI Salary (Puleo; 1.5 mo, 1.5mo, Macmahan; 1.5mo, 1.5mo, Righman?) 30 Tech Salary5 Travel2.5 Fringe1210 Overhead Total 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.