Charting the Future
Modeling and mapping software and GIS use in erosion control
By Tara Beecham
Used at construction sites for years, geographic information systems (GISs) and modeling and mapping software are taking a central role in erosion control planning and design today. With 3D graphics, animation, and projection detailing what a present site will look like years into the future, project engineers are making use of these technologies to save time and money as they work to control sediment and monitor water quality onsite before problems begin, keeping projects streamlined and on track.
This is no surprise to those who’ve seen this technology advance in leaps and bounds. Richard Phillips, a Williamsburg, VA-based professional engineer who has worked as a consultant in private practice for more than four decades and is currently the senior civil /structural reviewer on the Code Review Team at the Department of Facilities Management at the College of William and Mary in Williamsburg, VA, first saw the possible effects modeling software could have for civil engineers in the industry’s early days.
“I was aware of the possible benefits before hardware and software was available. I purchased my first computer in 1983 and immediately began seeking applications in terrain modeling, structural analysis and hydrology. At first there was very little available, and we tried writing our own,” he says. “As systems became available, it allowed individuals (sole practitioners) to compete with larger firms.”
It’s important to understand the role software has to play on a project site.
“The software is merely a tool. The engineer has to understand the problem and the limitations of the software. It is relatively easy to put numbers in and get numbers out. The operator has to understand what makes sense,” says Phillips.
He relates the example of using HydroCAD Software Solutions modeling software as part of the development of a Virginia-based shopping center about six years ago.
“It required the clearing of approximately 27 acres and the movement of more than 175,000 cubic yards of material. Storm drainage from offsite discharged uncontrolled on to it and flowed across it through a wide ravine, which was to be filled to a height of 30 feet,” he says. “HydroCAD allowed me to draft a mass grading plan, diverting the offsite runoff around the work area and collecting the onsite drainage into a series of sediment basins, which were shifted as the grading progressed. Because of its modeling capabilities, I could predict expected flow and design the required storage with outlets to control the discharge to protect the downstream channel during construction. While I worked on the construction-phase grading and erosion control plan, another engineer using HydroCAD developed the post-construction stormwater management system consisting of retention and infiltration ponds.”
One of the site’s challenges, explains Phillips, was its location adjacent to “the protective area of a municipal water supply. Downstream erosion was occurring due to the concentrated flows introduced by prior offsite construction, so we had to mitigate for that damage.”
The versatility of the product proved beneficial in terms of erosion control. Phillips, who had used HydroCAD since before its official release in 1986, expected this on the project.
“I have used it on projects in New Hampshire, Maine, Virginia, Delaware, and North Carolina,” he says. “I have used it to design projects and to review the work of others. HydroCAD is flexible and powerful; a skilled engineer can replicate a great variety of situations.”
Steep Slopes and Large Storms
Extreme weather events, steep slopes, and difficult soil can combine to become a formidable obstacle for any construction project. To face these challenges, the Portsmouth, NH–based Maguire Group Inc. also turned to HydroCAD modeling software.
“Recently, Maguire used HydroCAD to perform a hydrologic analysis of a commercial development on St. Thomas in the US Virgin Islands, which included two new commercial buildings and a building expansion, parking, and other infrastructure on a 50-acre site,” says Marisa DiBiaso, a senior civil engineer at Maguire Group. “HydroCAD was used to model the complex pre- and post-development hydrology of the site because of its user-friendly interface that allowed the model to be easily organized while enabling us to analyze a wide variety of drainage conditions.”
Site design for the ongoing project, which is currently in the permitting phrase, began in 2010. The site’s environment required extensive planning.
“The biggest challenges for this project were the high runoff volume produced by the steep slopes, low permeability of natural soils, and the 100-year design storm,” says DiBiaso. “The 100-year design storm is much larger in the Virgin Islands than most other areas of the US due to tropical climate in the Caribbean.”
Having used HydroCAD modeling software for several years, Maguire decided to use the product in an erosion control capacity at the St. Thomas site.
“The proposed drainage design required capturing runoff from a large area of steep upland and conveying the stormwater through the site to a large detention pond. To prevent erosion of the steep slopes, collection swales and a large closed drainage system were designed using HydroCAD. HydroCAD calculates stormwater flow depth and velocity, which are critical pieces of information when it comes to erosion control,” says DiBiaso. “The large detention pond also was designed using HydroCAD to detain the water-quality storm and attenuate stormwater discharge. In particular, the use of HydroCAD to model the outlet structures of the pond was critical to ensuring a safe design that allows for sedimentation to occur in the pond and prevents erosion at the discharge point.”
Stormwater management capabilities coupled with previous performance were the primary reasons selecting HydroCAD as a tool made sense for this project.
“I have been using HydroCAD for about seven years on over a dozen projects ranging from commercial/industrial sites to landfills to highways,” says DiBiaso. “I’ve been very happy with the results and have found HydroCAD’s online courses and webinars to be very beneficial.”
|Photo: RICHARD S. PHILLIPS
At this Virginia site, modeling helped in developing a mass grading plan to divert stormwater runoff.
|Photo: FAIRFAX COUNTY, VA
Part of Fairfax County’s flood monitoring system, which sends early warnings to personnel.
Erosion control is closely tied in many ways to site design, from protecting a site from sediment runoff to shaping proper drainage as well as countless other measures of defense. In fall 2011, Strategic Land Services based in Suwanee, GA, estimated a 1,000-acre new state park in Gainsville, GA, which will feature boating areas, hiking sites, and RV camping locations. Strategic Land Services used Dallas, TX–based Vertigraph’s SiteWorx software program during the estimation stage of the Don Carter State Park project. The software can digitize existing and proposed contour lines, spot elevations, project boundaries, and other areas. Once a digitized blueprint is created, the program can calculate cut and fill volumes and other data. The program can demonstrate how proposed site elevations can be adjusted.
Information in the printed or onscreen reports include a 3D graphic representation of both the site as it currently exists as well as the proposed site.
At Don Carter State Park, John Plont, an estimator at SLS, used SiteWorx to calculate fill and “how much cut, fill, import, or export of dirt is needed to build the project,” he says. He has used SiteWorx OS on a half-acre site with 1,500 cubic yards of earthwork—the La O’wn Academy in Roswell, GA—as well as on the Don Carter State Park, a 1,000-acre site with more than 150,000 cubic yards of earthwork. “I’ve found SiteWorx OS to be very versatile and easy to use,” says Plont.
The landscape at the Don Carter State Park provided a variety of challenges. “The existing terrain is very hilly. There are a lot of cut-and-fill areas to calculate. It had multiple takeoff pages to run calculations on. The project was so large, I had to break it up into 14 different projects,” says Plont. “Most of the projects are one sheet; this one was on 14. I was in that program [SiteWorx] working on that project for two weeks.”
For Plont, who says he uses the program almost daily, the decision to utilize SiteWorx for the park estimation was simple. “It cut our estimating time drastically, and it is a tremendous value for the money and has excellent technical support,” he says.
Monitoring the Difference
The Patton Creek Watershed Analysis project is taking place in hilly suburban Hoover, AL, where the land use is approximately 70% heavily wooded residential neighborhoods and approximately 30% commercial. In 2009, the city contracted Hydro-Engineering Solutions, which in turn contracted RainWave to use its monitoring software to collect data and issue reports at the site as the city sought to develop its stormwater management program (SWMP). “The city is required to develop a SWMP to maintain compliance with its NPDES [National Pollutant Discharge Elimination System] Phase I permit,” explains John Curry, a licensed engineer and president of Hydro-Engineering Solutions based in Auburn, AL. He says one goal the city had was “to differentiate what was coming from them as opposed to what was affecting them from adjacent municipalities.”
Rod Long, the city engineer for Hoover, explains that vegetation or decomposing vegetation had caused low dissolved oxygen levels. “We’re using in-stream monitors. One is in the northern part of the city attached to the bridge wing wall—a sonde with five sensors on it,” says Long. “Water-quality parameters include dissolved oxygen, depth of water, pH, conductivity, and temperature. Conductivity and pH changes can tell you something is in the water that shouldn’t be there.”
He says the RainWave system, in conjunction with the in-stream monitors, has helped the city identify potential water-quality problems in Patton Creek.
“RainWave gives us data we never had before,” says Long, noting that going out the day after an event and determining 4.5 inches of rain had fallen doesn’t tell the complete story if, for example, that much rain fell over the course of just a few hours. “If you have an event, you can pick out a study area and actually study an event after it happened,” he says. “This gives us an opportunity to have better control of the rainfall data that we’re trying to analyze. They’ve got the data everywhere. You can go out on a construction zone, and after a three-quarter-inch event, stormwater alerts go out and you check all your erosion control. We get 50 to 55 inches a year here. Most of our rain is heaviest in the winter months.”
Dewayne Smith, consultant for the city’s stormwater management program and senior engineer at Hydro-Engineering Solutions, says the NPDES permit required the city to collect grab samples on a quarterly basis for dry weather and wet-weather events for a laundry list of parameters.
“It was quite expensive,” he says. “Patton Creek has a TMDL [total maximum daily load] established for organic enrichment and dissolved oxygen. The TMDL attributes the source nutrients to be from leaking septic tanks and urban runoff. We requested that the state consider discontinuing the grab-sampling methodology and initiate continuous in-stream monitoring.”
Set points in the basin are monitored continuously. Curry describes how the RainWave system has been used to help evaluate water quality at the site where 10 monitoring points are evenly distributed throughout the basin area: “It can send the rain distribution to the model. Now we’ve got better data to make better decisions. You can see how the stream reacts to the rainfall data. We definitely know this is a discharge without rainfall. We can track them up to whatever the source might be.”
Long says that when a localized flooding event occurred within a 40-acre area, he was able to contact the company to pull up data in that specific area for that time period. Smith says that areas that are monitored could also be compared from year to year, allowing site managers to determine “are things getting better or are things getting worse. It is truly basin specific.” For example, Smith says the canopy at one location had heavily influenced a rain gauge, but using RainWave’s monitoring eliminates the potential for error in that regard.
Smith says the innovative tools that the Hoover is using for its stormwater management program are being used as an example now for other municipal separate storm sewer systems (MS4s) in the state of Alabama.
“It’s kind of a quality assurance for them,” he says, referring to the city of Hoover. “They can check on a developer to make sure it isn’t causing any harm to their MS4.”
Curry describes the type of monitoring that RainWave does for construction areas and instances when an alert can be issued. “Say you’re going to clear a right of way for a road. We can monitor points along that linear project. It could be for a roadway or it could be power lines. We’ll monitor several points along the cleared area,” he says. “The system will notify the project engineer or inspector to inspect the BMPs on the project when the permit threshold is reached (0.75 inches in Alabama). That’s all part of the NPDES permit. The system will kick an e-mail out to whoever is going to be doing the inspections.
“Let’s say that you’ve got a project that’s got a year duration, and we catch those storm events as we’re monitoring using the daily, monthly, and alert system. We can use a model such as the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) system to determine how much sediment may have moved off the site. It’s pretty neat.”
Reminders such as this can help keep a construction project on track, allowing personnel to concentrate on daily tasks yet receive automated alert reminders when rain events that can affect erosion control occur. In Hoover, a construction engineer contacted the Hydro-Engineering Solutions after a severe June 2010 rain event where readings showed 2.92 inches of rainfall fell in an hour. When the city engineer contacted Hydro-Engineering Solutions, the company was able to use the data collected to determine that the storm was a 25-year, one-hour-storm event.
“This rainfall caused some local flooding,” says Curry.
Joey Nunnally, construction engineer at the Baldwin County Highway Department, describes how the alerts have been used regularly in his area, particularly following a single rain event.
“We had some failures in our BMPs. We had an upset condition where we could be in violation of some rules and regulations,” he says referring to requirements set by the Alabama Department of Environmental Management (ADEM). “If the size of the event was great enough, the ADEM will just say to fix it and go forward.
“The documentation helped us prove that the event was greater than what it was designed for, and it prevented us from receiving violations.”
Nunnally has used these alerts regularly in his area since 2010. “All of us have Blackberries on our hips now so we can receive e-mails. I get these updates via e-mail, which is very nice,” he says, explaining that he initially provided RainWave with specific locations where he wanted monitors to be and now he doesn’t have to worry about the amount of rain that a project is getting because he will receive a report with an update.
“The inspectors really like the daily reports we get every time it rains. The reports come via e-mail so it doesn’t matter where you are or what you’re doing, you know how much rain your project received,” he says. “This is extremely helpful during a large rain event or a long weekend where a typical rain gauge may have been completely overwhelmed and therefore not giving you an accurate reading.
“You also don’t have to worry about the gauge getting damaged or vandalized as you do with a typical rain gauge. The biggest benefit for me has been the documentation and reports we can send to ADEM as backup data during an upset condition. The reports helped Baldwin County avoid violations that otherwise may have been more severe.”
A Changing Tide
Tracking patterns of erosion along waterways and comparing the data as well as recording the condition and location of BMPs on a project site are just a few ways monitoring software and GIS can be used in an erosion control capacity. Water-quality monitoring as it relates to disturbed soil and rain events that can affect BMPs is another.
Approximately one year after Hurricane Isabel damaged areas of the 400 square miles of Fairfax County, VA, county administrators began a search for a system that would improve stormwater monitoring for a variety of waterways throughout the region.
“There areas along the Potomac that are subject to tidal flooding. We only had one depth sensor on one of our dams at that point,” says Don Lacquement, an engineer in the Fairfax County Maintenance and Stormwater Management office, who is the project manager for the High Sierra Electronics monitoring system that was selected for the project. “We put HSE monitoring systems on the state-regulated dams to supplement the monitoring requirement that comes with the emergency action plans. As specified in the plan, you’re supposed to provide continuous monitoring once water levels reach set values.”
The county wanted to continue monitoring during a storm event, while saving money as well as protecting workers. Lacquement explains that by using an electronic monitoring system, the county would not have to have a worker at every county dam throughout a dangerous storm event.
In March 2008, Grass Valley, CA-based HSE installed its Flood Warning System for Monitoring High Hazard Dams and began a two-year maintenance contract for the county project. US Geological Survey information culled from stream gauges is used to monitor waterways such as creeks, but six PL-566 dams, 14 other state-regulated dams, two areas subject to tidal flooding, and a single area that is subject to flash flooding are monitored throughout the county using the HSE system, Lacquement explains. Lake Barcroft, a large private lake in the area, is also monitored by the system.
The system’s remote gauges report by VHF radio to the county’s base station computer, which runs DEC DataWise software. In addition to regular timed reports, the rain gauges report each millimeter of rainfall to the base station, according to HSE. Water-level sensors report changes in level chosen by the county; Fairfax County has set alarm criteria in DataWise for the new gauges, including rainfall levels, water levels, and the rate of water level rise at the dams. Personnel receive alerts by text message and e-mail.
The county intends to utilize the system, selected by committee based upon such criteria as proposed cost, instillation time, and references and installed in three phases, on a long-term basis.
“We may supplement maintenance to have more options in short-term emergencies,” says Lacquement. “You have to know a fair amount to troubleshoot these things. High Sierra has been very responsive.
“There’s no break in our plans for monitoring, and we do some maintenance in house. We troubleshoot. We’ve taken some of it upon ourselves. If it’s really complex, then we’ll bring in their expertise.”
Storms have put the system to the test. “It’s had severe rain events, and it has been very helpful. It gave us early warnings when predicted events turned out to be more significant than forecasted. It helps,” says Lacquement. “There’s a lot of pieces that go into flood monitoring and evacuation, and it’s a very helpful tool in the arsenal. We’re very fortunate to have it.”
Meeting Higher Standards
Kentucky’s Lexington-Fayette Urban County Government (LFUCG) also looked to software to meet compliance standards.
“In 2010, LFUCG selected Accela Automation web-based enterprise software from Accela Inc. to improve the city’s water-quality management and to facilitate compliance with US environmental regulations,” says Paul Davis, corporate communications director for Accela. “Part of the impetus came from a 2008 lawsuit by the US Environmental Protection Agency, citing LFUCG’s lack of compliance with EPA and Clean Water Act requirements. As such, LFUCG’s Division of Water Quality now uses Accela Automation to streamline and manage all activity relating to the inventory, inspection, repair, and maintenance of sanitary and storm sewer systems, and to consolidate information that previously tracked more than 16,500 records annually, across 22 databases.
“LFUCG also uses Accela Automation for erosion and sediment control [ESC] inspections and preventative maintenance schedules. ESC noncompliance violations are also handled by LFUCG’s Environmental Policy group using Accela Automation.”
In addition, to meet compliance standards, the county government has used the system in improving workplace efficiency.
“LFUCG serves a population of over 250,000 in the urban service area—with about 50 mobile workers across all areas, including management of ESC, using Accela Automation as a single point of access for data sharing and workflow, enabling more efficient monitoring and reporting in compliance with EPA and Clean Water Act requirements,” says Davis. “Deployed in 2011, the system now automates major aspects of the Division of Water Quality’s operations, allowing the division more effectively to review, approve, and track construction projects; receive, investigate, and prioritize requests for service; generate and assign work orders and reports and automate work scheduling; build an easily accessible asset library and maintenance history; and regulate discharge of materials into water assets, including tracking and monitoring of erosion sites, in order to prevent stormwater pollution.”
Two aspects of the software that were considered during LFUCG’s software selection process were the Accela system’s advanced GIS mapping, which, Davis explains, “tightly integrates with ESRI’s ArcGIS for Server software” and mobile functionality.
Redlands, CA–based GIS giant ESRI’s ArcGIS for Server software, which appears in basic, standard, and advanced editions, allows users to take the site information they generate and make it more readily available within a network. Geodatabase replication, geodatabase management, web mapping applications, and geoprocessing are examples of the program’s capabilities.
“Field-based inspection and maintenance teams can easily and consistently track the location and status of sanitary sewer and stormwater data, further boosting preventative maintenance of critical water-quality assets,” Davis says of LFUCG. “These workers can also access the same data as LFUCG’s back-office staff and enjoy a similar user experience on their devices—including maps, current work assignments, and historical information. This enables them to maximize staff schedules, and to perform key functions and reporting at the asset site, rather than spend hours in the office for data entry or other coordination. Operating from a centralized database, Accela Automation allows users to share information across departments and to easily configure application types, business processes, fees, and reports based on the needs of the specific worker or situation.”
He discusses how this could help a project site where significant erosion has been a concern. “At an erosion site, for example, they can log in the particulars of the problem and access the history of a particular site in terms of previous work done, workers who previously handled the problem, equipment used, the equipment’s maintenance history, and so on. All of this boosts efficiency by allowing field staff to identify, address, and rectify erosion problems quickly.”
With the growing need for erosion control solutions to meet ever-changing regulations, advances in modeling software and GIS, coupled with experienced project design and management, can only promise a brighter future for the industry.
Tara Beecham is a frequent contributor to Forester publications.