Interview with Erin Rothman

Could you tell us briefly about your career path and your current role in StormSensor?

Before I founded StormSensor, I was VP, principal scientist, and managing principal at three environmental consulting companies, one of which was my own, mostly working with real estate developers to remediate contaminated sites in urban infill environments. I enjoyed the work, but not the industry. No one hires environmental consultants because they want to; they do it because they have to, and that makes it less fun. I wanted to do something that benefited the environment, but in a way that excited people.

In addition to managing my own projects and teams, I worked with our stormwater group to improve profitability. That’s when I saw how many opportunities we had as an industry – not just in the industrial and construction spaces – but on the municipal side as well. I actually saw some of the biggest opportunities, especially within municipalities.

I came up with StormSensor as a joke, really, because it just seemed so obvious that having real-time data made so much more sense. But this was back in 2010 or so, when IoT was very new, and when I didn’t have any hardware or software experience.

In 2015, I took a product management class with StormSensor as my product. As part of the program, I had to interview hundreds of customers, and through that process, I learned that (1) we don’t have any information about how water flows through our storm and sewer systems, with the exception of models and temporary sensor locations, and (2) a lot of cities thought that real-time data made a lot of sense…if only it was accessible, available, and meaningful.

So, I founded StormSensor in 2015 with a simple vision to create the ‘Google traffic maps of sewers and stormwater systems.’ Our solution set out to meter the last unmetered utility with IoT sensors deployed across cities to track real-time temperature, flow, and weather conditions.

I hired my first employee in 2016 and my second in 2017. I raised my first real fundraising round in 2018, when we deployed our first prototype sensor network. I raised another round in 2020, when we doubled our team and deployed sensor networks in every region in the country. 2021 has been absolutely amazing in terms of growth, both with our customers and our team.

How can innovative stormwater management systems help cities mitigate climate-related risks?

Simply understanding how our critical infrastructure functions during normal conditions, as well as under stress from heavy rains and rising water levels, gives us the fundamental knowledge necessary to do everything from streamlining maintenance to responding to severe events proactively, as well as accurately sizing our capital improvements.
Because extreme weather events are becoming more common, it’s critical that we understand our vulnerabilities in advance in order to respond accordingly.

And if you think about it, stormwater infrastructure manages – and is impacted by – so many different factors. This includes sea level rise, water quality, flooding, clogs and backups, overflows, and limited maintenance due to limited resources and limited information.
Incorporating high-resolution data capture (“high resolution,” meaning in terms of both frequency and spatial density) and applying analytics to get to the core of the issue provides visibility into your systems as they stand currently. This data can also highlight vulnerabilities that you might otherwise miss by just applying models and assumptions.

Can StormSensor solutions help address problems caused by combined sewer overflows?

StormSensor’s data networks allow cities to capture the real-time, empirical data that is critical for accurately reporting CSOs, designing and implementing an effective long-term control plan, and ensuring that any engineering estimates and associated solutions account for the actual volume of water discharged from the combined system.

Our notifications provide forecasted and real-time alerts of active CSOs, which can be used to support public notification requirements. The data are easily consolidated for quarterly reporting to the U.S. EPA.

One of the trickier aspects of some combined sewer monitoring programs is that so many discharge into tidal waterways, making quantification difficult (the same can be said for stormwater systems as well). We apply targeted algorithms that, to put it simply, remove the tidal impacts and allow us to measure just the overflow or the discharge.

By doing so, we can accurately quantify flow events, ensuring that the volume and the frequency of overflows is properly tracked and monitored. That data can then be used to develop your long-term control plan, ensuring that the full volume of CSOs is addressed by the plans, some of which can be incredibly costly to implement.

As the sewers are separated, monitoring stormwater runoff from the new storm systems can be used to document progress by quantifying the volume of runoff routed away from the treatment plant.

How does the digitalisation of storm or sewer systems compare with solutions based on green infrastructure in terms of effectively tackling flooding and water quality concerns related to stormwater? What about in terms of implementation and maintenance costs?

Using a data-driven maintenance approach helps municipalities meet regulatory requirements while reducing unnecessary maintenance costs. Maintenance can be targeted to known issues on an as-needed basis rather than at predetermined service intervals. For example, bioretention cells lose functionality as infiltration rates decrease. With StormSensor, a stormwater manager can remotely review and assess the performance of multiple assets during rain events.

Our clog alert automatically detects and alerts staff to potential issues, reducing the frequency of flooding. Targeted catch basin cleaning and pipe jetting based on known sediment loading will help to improve overall system performance while minimizing costs. Lastly, our temperature data can help municipalities identify inflow and infiltration (I&I) locations which, if addressed, reduces wastewater treatment costs and the need for system-wide underground camera inspections.

Our sensors can be installed upstream and downstream of BMPs, and they would remain in place after construction is complete. In general, while having in situ sensors in all types of GI may not be feasible, pre and post-construction monitoring is appropriate for any type of GI. StormSensor’s networks are more typically deployed by cities to take a watershed and network-based perspective on flows, and data collection within the sewer system itself is also highly recommended.

Can you explain what the StormSensor Risk Index is?

StormSensor’s Urban Flood Risk Index, or SURFR™, is a map view of your community that incorporates geophysical and socioeconomic spatial data into a holistic risk index which can be used to identify risk-prone zones within your community. It takes into account a series of influencing factors, including impervious surfaces, population density, income, flow accumulation, etc. The maps are broken into the spatial resolution of your choice: census tracts, modeled watershed basins, or grids. We call these “risk management zones” or RMZs. The RMZs are compared relative to each other, both per parameter and then with all parameters combined.

The maps themselves are interactive and include a dashboard analysis of every RMZ – for example, which parameter(s) drive the risk score – and they can also integrate your GIS data. It’s eye-opening to see how these compare to FEMA and how the outcomes align with expectations based on real-world experience.

SURFR™ is also a useful tool that helps us prioritize locations to install data networks, highlighting the areas that would have the greatest impact if we only had visibility into that storm or sewer system.

Is intelligent wastewater and stormwater infrastructure for large cities, or can smaller communities afford to become smart as well?

Anyone can use it! That was a key objective of ours from the outset and remains the case today. So many of the solutions that are on the market right now are so incredibly expensive, which limits their accessibility. We believe that getting everyone access to the data, and providing everyone with the information they need to make informed decisions, drives economic and social benefits across communities. We’ve deployed networks in cities with 5,000 people, as well as in cities with 700,000 people.

What role do you see for smart stormwater solutions as climate-driven extreme events become more frequent in the future?

I think these solutions will become even more critical as extreme events intensify. Consider how effective a given storm or sewer system is under normal conditions. As those systems age, they experience more problems, from more frequent maintenance needs to more backups and overflows. Add in more extreme storm events and these systems – many of which are at their limits right now – will not operate sustainably.

Just imagine if we knew exactly where those issues are, exactly how different events affect these incredibly variable and unique systems, and it was standard practice to drive operation and design based on incorporating resilience into our critical infrastructure through digitalization. We’ve invested in smart technologies across every other utility; it’s time to do the same in stormwater.