Monitoring Scour Critical Bridges (2009)

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29 The survey asked bridge owners various questions about their experiences with fixed scour monitoring instrument systems. This chapter includes a summary of their responses, as well as trends from the survey and the literature research. The detailed responses of the survey respondents experience and suggestions can be found in Appendix C. REASONS FOR INSTALLATION OF MONITORING SYSTEM The bridge owners were asked to indicate why they installed fixed scour monitors at their bridges. Thirty-nine of the 56 sur- vey respondents indicated that their bridges had scour critical ratings. Sixteen indicated research projects, seven bridge replacements, and three other reasons (an observed scour hole, a sudden settlement of a pier, and the potential for a gravel pit failure downstream of the bridge). Other factors that contributed to their decision to use fixed scour monitors at their bridge sites included: • The importance of the transportation system • Scour evaluations • A history of scour • Pier failure • Spread footings • Short piles at the piers • Unknown foundations • High water velocities • Public safety concerns • A need for continuous monitoring during storms • Observations during routine inspections • Bridge is scheduled to be replaced • Stage construction requirements • Difficulties involved with hydraulic or structural counter- measures • Relatively low ADT • Potential headcut from downstream controls • Research team insisted on monitoring. As shown in chapter three, Table 4, the NBIS Item 113 Rating for Scour Critical Bridges ranged from 2 to 8 on the sample bridges that are being monitored. There was only one rating of 2 and seven ratings of 3, which indicate that a bridge is scour critical. The other bridges were rated 5 to 8, which are not scour critical ratings. Not all bridges reported Item 113 ratings, and it is not known if some of the 39 bridge sites that reported monitors were installed as a result of scour critical ratings were indicating there was a scour problem and/or did not reference the NBIS rating system. Additional scour countermeasures can also have been installed at these bridges to remove them from scour critical status or the bridges can have been replaced and they reported the new coding. Fewer than half (47%) indicated that the scour monitoring data obtained had been useful for changes or verification of their bridge scour ratings, whereas 51% said it had not been useful. Alaska mentioned that the scour monitors had identi- fied large dune bedforms and seasonal sediment “starvation.” The large annual scour and fill cycles have been recorded in the monitoring data and have been used to evaluate the predictive scour equations. California stated that the data con- firmed that the scour did not adversely affect one particular bridge and that the lack of an alarm indicated that the down- stream headcut was not migrating toward the bridge. OFFICE RESPONSIBLE FOR MONITORING The office responsible for scour monitoring varied, but was most often the structures or maintenance group of the state DOT. Others that were mentioned included the state hydraulics group, universities, the USGS, and consultants. PURCHASE, INSTALLATION, MAINTENANCE, AND REPAIR COSTS The bridge owners provided information on the costs of the scour monitoring systems. This can be found in Appendix C. A summary of estimated cost information based on the survey results can be found in Table 6. It was developed using the format of the monitoring cost table found in FHWA HEC-23 (Lagasse et al. 2001a). The costs of the scour monitoring installations varied widely owing to different site conditions, the type of contract, and the method of installation. The survey question on installation costs asked the respondents to provide information on the cost of materials and the labor, per monitor location and/or the total cost. Cost information was provided by 11 different states representing 41 bridge sites. The cost information for materials was the data most often provided by the survey respondents. The installation, CHAPTER FOUR EXPERIENCE WITH SCOUR MONITORING SYSTEMS

operation, maintenance, and repair costs are more difficult to ascertain. Instrument costs generally include the basic scour moni- toring instrument and mounting hardware, as well as power supply, data logger, and instrument shelter/enclosure, where applicable. This cost cannot include miscellaneous items to install the equipment such as electrical conduit, brackets, and anchor bolts that can be included as part of the contractor installation cost. Some of the material costs included other devices such as water stage, and one bridge included moni- toring, maintenance, and repairs during a 2-year period that the bridge is expected to be monitored. The installation costs were often not available because the labor was provided by students or state maintenance groups, or the cost was included with other construction items. Scour monitors can be installed at certain sites by the state main- tenance group with equipment it owns. More complicated installations and sites can require specialized contractors and construction equipment to install the scour monitoring devices. Maintenance and repair costs were only given by one respondent, Florida DOT, District 7. For their sonar scour monitoring system the operation and maintenance was esti- mated at $18,000, and inspection and repairs were about $9,000. They stated that these were the result of durability problems with the sensors and to vandalism. The respondents provided numerous comments on maintenance and repairs. The general comments on the cost of maintenance ranged from modest to expensive. Repair costs were estimated to be expensive, particularly for underwater divers for the reinstal- lation of sonar monitors. The installation of the monitors can be under a bridge rehabilitation, research, or emergency project. When that project is completed and the funding ends there can be no mechanism under which to fund long- term maintenance and repairs. Comments included the need for a commitment to maintain the equipment and also a main- tenance contract with a firm familiar with the equipment 30 that can make repairs in an expedient manner. Traffic con- ditions and lane closures were also cited as difficulties in maintaining the monitoring system. Contractor installation and repair costs also vary greatly in different regions of the United States. The cost of the scour monitoring installations can vary dramatically owing to different factors such as site conditions, the experience of the personnel installing the equipment, the type of contract, and the installation requirements. Larger bridges and deeper waterways are more expensive to instru- ment than smaller bridges in ephemeral or low water crossings. Scour monitors can be installed at certain sites by the state maintenance group, another agency with equipment it owns, or by students. More complicated installations and sites can require specialized contractors and construction equipment to install the scour monitoring devices. Factors that contribute to increased scour monitoring instal- lation, inspection, maintenance, and repair costs include larger bridges; complex pier geometries; bridges with large deck heights off the water; deeper waterways; long-distance electrical conduit runs; more durable materials required for underwater tidal installations; the type of data retrieval required (i.e., Internet or satellite); lane or bridge closures and maintenance-of-traffic; and installation and access equipment such as boats, barges, snooper trucks, drills, and diving teams. Most recent installations of fixed instrumentation have used remote technology to download data to avoid repeated visits to the bridge site. Although this increases the initial equipment cost, it can substantially reduce the long-term operational costs of data retrieval. Site data retrieval involves sending crews to the bridge and access can include security clearance, lane or bridge closures, and equipment such as snooper trucks or boats. Remote technology can also increase safety to the traveling public because it permits real-time monitoring during the storm events that can result in earlier detection of scour. Typed of Fixed Instrumentation Instrument Cost with Remote Technology ($)* Instrument Cost for Each Additional Location ($) Installation Cost Maintenance/ Operation Costs Sonar 12,000–18,000 10,000–15,500 Medium to high; 5- to 10- person days to install Medium to high Magnetic Sliding Collar 13,000–15,500 10,500–12,500 Medium, minimum 5-person days to install Medium Tilt Sensors 10,000–11,000 8,000–9,000 Low Low Float-Out Device 10,100–10,600 1,100–1,600 Medium; varies with number installed Low Sounding Rods 7,500–10,000 7,500–10,000 Medium; minimum 5-person days to install High Time Domain Reflectometers 5,500–21,700 500 Low Medium *Cost per device will decrease when multiple devices share remote stations and/or the master station. TABLE 6 ESTIMATED COST INFORMATION

31 EVALUATION OF BENEFITS The majority of states mentioned safety for the traveling public as the main benefit of scour monitoring systems. Additional benefits included a reduced number of underwater and/or regular inspections, early identification of problems prior to a diving inspection, and insight into site-specific scour processes. In several states the system is a component of a comprehen- sive program that includes a Plan of Action for emergency conditions and underwater inspections. A point was made that the system serves to warn of a problem at the bridge site; however, response time and engineering judgment by those persons responsible for the bridge are the most important part of the alarm system. VERIFICATION OF SCOUR PREDICTION The bridge owners were asked if their scour monitoring data had been useful in verifying scour prediction equations. Alaska, Georgia, and Hawaii provided detailed responses and have published papers on the subject. Several other states also provided comments on the usefulness of the data. Alaska The USGS in Alaska responded that the scour monitoring data have been useful in verifying scour predictions. It reported that the data were useful in separating the components of scour and to evaluate the predictive equations. The variation in the data from the seasonal bed elevation ranged from no change to large changes for the 20 bridges instrumented with sonar and water stage devices. They also reported short period scour associated with high flows. In addition to the near real-time data, channel bathymetry and velocity profiles are collected at each site several times per year. The Cooper Delta Bridge No. 342 has eight instrumented piers and they noted that this provided visualization of scour for the entire bridge cross section. The scour monitoring data from the instrumented bridges in Alaska has fostered a number of USGS reports (Conaway 2005, 2006a,b). The USGS in Alaska noted that bridge scour monitoring is being used to assess real-time hazards and that it also illus- trates the complexities of streambed scour and the difficulty of predicting scour using existing methods (Conaway 2006a). The stage and bed-elevation data at the Old Glenn Highway Bridge over the Knik River near Palmer, Alaska, was com- pared with results from predictive scour calculations using variables generated by a hydrodynamic model, the USGS’s Multi-Dimensional Surface Water Modeling System. Chapter six of this report contains the case history and a discussion of the observed scour for this site. Conaway reported that the data of the Old Glenn Highway Bridge showed an annual cycle of channel aggradation and degradation to an equilibrium level that is punctuated by shorter periods of scour and fill. The annual vertical bed- elevation change exceeds 6 m (20 ft) at the bridge. Data from a pier-mounted sonar together with hydraulic variables measured during high flows and variables computed with a multi-dimensional hydrodynamic model were used to evaluate seven predictive equations for live-bed contraction scour and two abutment scour computations. Two scour events were simulated with the hydrodynamic model; one related to rainfall, the other for a period of increased glacial melting. Streambed scour for these two events varied con- siderably in timing and duration, although both had similar streamflow discharges. Total computed scour exceeded measured values by 40% to 60% depending on the equations selected. Conaway concluded that the long-term monitoring data indicate the scour at this site is the result of changes in hydraulic variables and is also affected by the timing and duration of streamflow, as well as the source of the high flow. He noted that these factors are not typically included in the engineering assessment of streambed scour. Georgia The Georgia Institute of Technology (Georgia Tech) and the USGS, in cooperation with the Georgia DOT and the FHWA, are conducting an investigation to improve regional bridge scour predictions by combining field monitoring, physical modeling in the laboratory, and three-dimensional (3D) numer- ical modeling of bridge scour (Gotvald 2003 and Sturm et al. 2004). The integration of these three components is intended to improve bridge scour predictions using one-dimensional methods. A report for Phase 1 of this project was published in 2004, and Phase 2 is currently in progress. Bridge scour field data were collected at four sites located in different regions of Georgia using fixed instrumentation and mobile instrumentation. The fixed instrumentation at each bridge included four to seven fathometers, one rain gauge, and one stage sensor. Two bridges were also instrumented with acoustic velocity meters. These field data were used to calibrate the physical and 3D numerical models. Two bridges were modeled in the laboratory. Sturm et al. reported that the field results revealed several important aspects of bridge scour processes including the dynamics of live-bed scour, simultaneous occurrence of contraction and pier scour, and the cyclical scour and fill associated with the tidal cycle. He noted that the field data also proved to be invaluable for comparison with laboratory model results and stated that this validated the need for addi- tional continuous and simultaneous measurements of scour depths and flow fields. Sturm concluded that the 3D model is a powerful tool for understanding the complex flow field at bridge foundations and the coupling between the flow field and measured scour patterns. They reported that comparisons of laboratory scour

depths with existing scour formulas highlighted some of the difficulties in scaling of scour depths from the laboratory to the field; however, a successful modeling strategy was applied. The laboratory model successfully reproduced the measured maximum scour depths in the field for both the bank-full and extreme flood events, and the details of cross-sectional changes immediately upstream of the bridge. The laboratory erosion tests illustrated the regional variability of erosion parameters and as the variability associated with sediment stratification at a particular site. Erosion parameters were successfully correlated with some easily measured sediment properties. Sturm et al. concluded that these advances in field data collection, 3D numerical modeling, and laboratory modeling of bridge scour, as well as in measurement and prediction of sediment erodibility properties, can be useful to improve scour prediction techniques. Phase 2 of the project will focus on contraction scour and the development of scour prediction methodology. Hawaii The Hawaii DOT funded a project that uses scour monitoring data to evaluate the accuracy of some of the FHWA HEC-18 scour equations. This work was conducted by the University of Hawaii in Manoa, Honolulu. In addition to their synthesis surveys, they submitted a paper called “A Validation Study of the Empirical Bridge Scour Equations” (Teng et al. 2005). Scour monitors were installed at two bridges in Hawaii. In January 2004 a storm was recorded by the sonar monitors at the Kaelepulu Bridge, and the field data were compared with the predicted scour from the existing scour equations. The U.S. Army Corps of Engineers HEC-RAS software was used and the analysis was done to simulate the flow con- ditions and predict the scour depths at Kaelepulu Bridge under the storm conditions. The predicted scour depths of 2.4 m and 3.4 m (8 ft and 11 ft) were larger than the recorded scour depths of 0.46 m (1.5 ft) near the abutment and 0.3 m (1.0 ft) near the center pier at the bridge. They noted that one possible reason for this large difference is that in the numerical simulation, they assumed that the streambed material was fine sand in order to obtain the most conservative estimate for the bridge scour. During the installation of the sliding magnetic collars at the bridge site, boring tests were conducted and boring samples at the site showed fine sand at the streambed surface but large coral rocks at deeper depths. For this case, the parameter K4 for predicting local scour at piers can be reduced. They noted however that even if they used the min- imum allowable value of K4, the predicted scour depth at the pier would still be about 4 times larger than the measured scour depth. For abutment scour, the empirical equation does not consider the size of the streambed material at all. They pointed out that other possible differences could be in the estimate of the flood hydrograph from the rainfall record and 32 of the geometry and dimensions of the stream reach near the bridge. Teng et al. reported that the results showed that the pre- dicted scour depth at this bridge based on the existing empir- ical equations could be more than four times larger than the recorded scour depth in the field. She pointed out that their study was only a preliminary study. The field data were col- lected at one bridge site from one flood event only; therefore, it is not sufficient for a validation of the scour equations. They noted that bridge scour is a very complex and difficult problem to model theoretically because it involves the inter- action of solid structure, movable bed material, and water flow. They recommended additional field monitoring and data collection at more bridge sites. Other States The remainder of the respondents did not provide any data in this regard; however, their comments on the usefulness of monitoring data for the verification of scour predictions are described here. California reported that tilt meters have been able to track the daily thermal movements and the influence of construction activities adjacent to the bridge site. This site experienced record flows in January 2005, but no alarms or excessive movements were tracked. The float-out devices at the site were not activated. Florida reported that it had observed the tidal scour and infill processes. Their scour monitoring instruments have recorded the movement of loose soil and its redeposition by the tidal change currents. Maryland reported that there was no significant scour recorded at any of the five piers being monitored. The velocity meter readings show that velocities have been low over the monitoring period, from 1999 to 2006, when the bridge was replaced. They noted that this has been useful in indicating that the bridge is stable, that bridge closures have not been necessary, and to ensure the safety of the traveling public. The New York State Thruway Authority reported that a change in the monitored streambed elevation prompted fur- ther investigation of potential scour at the bridge. The results showed that the footing of the bridge was not exposed. The USCOE Cold Regions Research and Engineering Laboratory reported that ice is not included in current scour prediction and the data it has collected on the Vermont bridge with instrumentation has been invaluable for developing numerical models and calibrating flume studies. Clark County in Washington State reported that “absolutely” the monitoring data have been useful for verifying the scour predictions.

33 INSTALLATION EXPERIENCE The type of contract used to install the scour monitoring systems varied and included bridge scour countermeasures, bridge rehabilitation, research, USGS projects, and emergency scour conditions. Figure 28 shows which parties were involved with the design, manufacture, and installation of the scour monitoring systems. The groups included the owner (in-house depart- ment), monitoring system vendor, contractor, and consultant. The monitoring system vendors manufacture the system or components of the system and can be responsible for or assist in the installation and calibration. The consultant would be a consulting engineering firm. The design and manufacture of the systems were done primarily by the monitoring system vendor, whereas the installations were done by a variety of groups including the bridge owners, the USGS, and contractors. Additional Scour Countermeasures According to FHWA HEC-23, scour monitoring can be used in conjunction with other scour countermeasures. Twelve sites reported the use of additional scour countermeasures at their bridges. These included hydraulic, structural, and portable monitoring countermeasures: riprap protection; stone-filled steel sheet piling around the piers; a downstream sheetpile check dam; lateral stiffening and bracing between the pier bents; crutch bents at the piers; and portable sonar monitors to confirm the measurements taken by the fixed scour monitoring devices. One bridge in North Carolina reported extremely severe conditions. Some areas near the bridge had scoured and filled as much as 16.5 m (54 ft). Water velocities were in the 3.7 to 4.6 mps range (12 to 15 fps). Numerous scour countermeasures were employed at this bridge and they included armor stone around the bents, new steel helper-bents, concrete cylinder pile helper-bents, gabion mats, A-Jaxs concrete armor units, and sand bag scour protection. Additional Instrumentation Most fixed scour monitoring installations included water stage sensors. Additional instrumentation included temperature sensors, velocity meters, inclinometers, and wind sensors. Most of these sensors were integrated into the scour moni- toring systems. The temperature sensors are used for sound velocity correction for the sonar scour monitoring systems. The installation at the Woodrow Wilson Memorial Bridge over the Potomac River in Washington, D.C., included four velocity meters and one water stage in addition to the five sonar scour monitors (Figures 29 and 30). 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% USGS 22 6 Contractor 3 6 10 In-House 11 6 Consultant 7 0 9 Vendor 38 36 20 22 25 Other 5 3 16 Design InstallationManufacture FIGURE 28 Parties involved in the design, manufacture, and installation of fixed scour monitoring systems. (Note: “Other” responses included various universities and federal agencies.) FIGURE 29 Elevation of the original Woodrow Wilson Memorial Bridge.

LESSONS LEARNED FROM STATES THAT USE INSTRUMENTATION A wide variety of responses were obtained when the bridge owners were asked about lessons learned from the use of fixed scour monitoring instrumentation. The majority of states expressed concern regarding the maintenance of the scour monitoring systems. They learned that maintenance needs of the system were often greater than anticipated. One state noted that the devices take readings and report real-time data, but that maintaining an opera- tional system was very difficult. An on-going maintenance contract with a firm having special expertise with the scour monitoring equipment was recommended by another state. They pointed out that the contract should cover the entire period of the monitoring effort. The scour monitoring selec- tion, design, and installation is only a small part of the endeavor. Developing and maintaining a response protocol and responsibilities, as well as long-term functioning of the system, were the major challenges. 34 The states also found the need to install more robust, protected devices. Several noted the need for stronger, custom- designed brackets. The materials used for the brackets should be carefully evaluated. The brackets could prevent move- ment, but be easy to remove to provide maintenance and repairs. Several states noted that the protection of the cables that transmit the data from the sensor to the data logger was their major concern, and that water, debris, and ice forces have interfered with the functioning of the system. One respondent noted that the scour instrumentation group was too dependent on a single individual for support and they needed to determine the proper alarm trip items for each substructure unit being monitored. They also reported that their systems were programmed to automatically call in if there was a scour problem. They found that no calls gave staff the assurance that there were no scour problems; how- ever, they noted that it could also occur when the system was not working. One state reported that the scour monitoring systems were more expensive than initially thought, but an alternative where physical countermeasures were used was impractical. They also noted that they can be used for the verification of the scour calculations, to demonstrate that a scour problem does or does not actually exist. CHALLENGES AND PROBLEMS Problems encountered during installation included difficulties in attaching the brackets to the substructure, working from a boat, climbing the superstructure, access to the river, traffic lane closure restrictions, budget limitations for staff overtime work, difficult installation requiring extensive equipment and experienced personnel, radio telemetry interference as a result of an in-line cellular telephone tower, and environ- mental impacts and disposal regulations for the excavation for the float-out devices. The parties involved in the maintenance, repair, and inspec- tion of the fixed scour monitoring systems can be found in Figure 31. The largest groups are in-house bridge owners and the USGS. Problems and issues after installation included the need for specialized equipment and personnel for maintain- ing the system; budgets that do not anticipate unscheduled repairs; the difficult logistics of the replacement of batteries; vandalism; high water velocities that cause excessive strain to the mounting brackets; power, communication, and van- dalism problems in remote locations; and the need for an instrument bracket that will withstand ice and debris, but is long enough to clear protruding footings. The various problems and challenges have caused a sig- nificant amount of uncertainty as to whether agencies will use fixed scour monitoring systems in the future. The survey FIGURE 30 Close up of velocity meter mounted on the fender of the Woodrow Wilson Bridge.

35 asked if they planned to use additional fixed or portable scour monitors in the future. Thirty-six percent of the respondents stated that they planned to use monitors, 19% said no, and 45% were not certain. INSTRUMENT RELIABILITY AND LONGEVITY Approximately 63% of the respondents reported that their fixed scour monitoring installations were operational. The remainder reported that the monitoring was discontinued, that the system needed repairs, was vandalized, or that the bridge was replaced. Appendix D, Table D1, includes infor- mation provided by the respondents on whether their systems are functioning. A wide variety of factors interrupted or damaged the fixed scour monitoring systems. Figure 21 in chapter three showed the percentages for numerous factors disturbing service. The most common problem was the debris flows and accumulation. Survey respondents were asked to comment on reliability and longevity of their scour monitoring systems. The com- ments on problems included vandalism, access limitations to replace batteries, marine growth, debris, and damage to the sensor attachments owing to high water velocities. The sec- tion on lessons learned in this chapter included a number of items on problems encountered and needs for future monitoring systems. Regularly scheduled maintenance and inspection proce- dures for their scour monitoring systems were reported by 63% of the respondents. The Florida districts reported that the under- water sonar sensors require maintenance or replacement one to two times per year as a result of marine growth accumulation. PROGRAMS, MANUALS, AND GUIDELINES CONCURRENTLY DEVELOPED Emergency Protocol An emergency protocol can be set up through a Plan of Action for a bridge or system of bridges, or through other documents. The respondents were asked to describe what they considered an emergency situation and what the emergency protocol would be for their bridge site(s). The majority of respondents stated that structural stability analyses were conducted for their bridge piers and abutments and thresh- old scour elevations were established that would trigger the emergency protocol, should they occur. Specific water surface elevations, or tropical storm or hurricane watches and warnings, were also used to determine if there were emergency situations. Emergency responses to these situations included visual monitoring, increased frequency for downloading the data of the fixed scour monitoring systems, underwater inspec- tions, bridge closures, and the design and installation of hydraulic and/or structural scour countermeasures. Most bridge owners reported that an emergency Plan of Action, similar to that developed by FHWA, had been estab- lished for their monitored bridge sites. General Protocol About half of the respondents indicated that they conduct independent checks to confirm the validity of the scour monitor readings. These independent checks were most often underwater diving inspections. The use of portable scour monitoring instrumentation was also reported. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% USGS 25 25 25 Contractor 2 24 In-House 24 23 25 Consultant 9 7 7 2 Vendor 8 9 4 Other 9 8 10 Maintenance InspectionRepair FIGURE 31 Parties involved in the maintenance, repair, and inspection of fixed scour monitoring systems. (Note: Other responses included various universities and federal agencies.)

Appendix G contains sample programs, guidelines, and manuals for fixed scour monitoring systems. ADVANCEMENTS AND INNOVATIONS Automated alarm systems can be installed as part of the scour monitoring systems. They serve to notify the owner, or designated parties if a scour threshold reading has been obtained. This information can be transmitted through a variety of forms from the bridge, and notification of a desig- nated scour reading can be sent to a pager, telephone, fax, or computer. The respondents indicated that these automated systems were included in about half of their installations; however, some of these systems were not activated. Often the owner prefers to have a person download the data in order to check existing conditions. There were few special innovative features or materials reported. Most of these were not in practice during the NCHRP project on fixed scour monitors (Lagasse et al. 1997), but were developed subsequent to that, and are described in FHWA HEC-23 (Lagasse et al. 2001a). The innovative features reported by the survey respondents included remote down- loading capabilities by means of telephone or satellite, water temperature sensors for sound velocity correction on sonar scour monitors, water stage sensors, and radio transmission of data from remote stations to a permanent facility. In chan- nels with high water velocities and/or tidal waters, the use of stainless steel (AISI 316) or aluminum mountings for the 36 underwater components were reported to be more successful than the polyvinyl chloride used during the NCHRP project on scour monitoring instrumentation. INFORMATION FROM STATES THAT HAVE NOT USED INSTRUMENTATION Bridge owners who do not use scour monitors were asked to indicate what were the problems or limitations for why they had chosen not to use this technology. They were also asked to discuss innovations and advancements they would like to see in fixed monitoring technology. The most common concern was the high cost of fixed monitors. This was followed by problems with reliability and their desire for little or no maintenance requirements for a monitoring system. Other factors that owners described as contributing to problems with fixed scour monitors included ice, debris, lightening, inadequate funding, the long time required for installation, the poor quality of the data, and dif- ficulties in the acquisition of the data. They also described various needs for their monitoring systems that included good reporting capabilities; remote access; negligible operating costs; and systems that can withstand extremely high tem- peratures, are protected from vandalism, particularly over ephemeral streams, have the ability to take measurements through silty and murky water, and devices where all parts are outside of the water.