Team isn’t just a word around here. It’s a commitment.

WSE is a team of passionate problem solvers who aim to have a positive impact on our industry, the environment, and our communities.


Jeff Johnson, M.S., P.E.

Jeff, co-founder of WSE, is an expert in the fields of hydraulics, sediment transport, and geomorphology, especially as they relate to public safety and natural resource protection.

Larry Karpack, M.S., P.E.

Larry, co-founder of WSE, is a problem solver who loves using his expertise in surface water hydrology and hydraulics to help clients address complex water management issues.

Bob Elliot, M.S., P.E.

With more than 30 years of practical experience modeling and investigating the many streams and floodplains within the greater Pacific Northwest, Bob specializes in and leads WSE's numerical hydraulic modeling program.

Chris Frei, M.S., P.E.

Chris is a senior hydraulic engineer with over 10 years of professional and academic experience working on complex hydraulic and water resource projects throughout the Pacific Northwest.

Dan Scott, PhD, L.G.

Dan is a fluvial geomorphologist who studies how wood, sediment, and water interact to shape river corridors.

Marissa Rohlfing, M.S., P.E.

Marissa has worked on hydraulic and hydrologic studies throughout the Pacific Northwest and beyond since 2015.

Colin Butler, P.E.

Colin joined WSE as a hydraulic engineer in September 2016 after completing his Bachelor's degree in Civil & Environmental Engineering with a focus in hydrology and hydrodynamics at the University of Washington.

Kaleb Madsen, M.S., P.E.

Kaleb joined WSE in the fall of 2017. He has a Master's in civil engineering from Washington State University.

Tim Tschetter, M.S., L.G., E.I.T.

Tim joined WSE in 2016. He is in the process of completing a Master's degree in Civil Engineering at the University of Alaska-Fairbanks with a focus on sediment transport and river mechanics.

Chris Meder, M.S., P.E.

Chris first joined WSE as an intern and returned in early 2020 as a junior hydraulic engineer after completing a Masters of Science in civil engineering focusing on hydrology and hydrodynamics at the University of Washington.

Sierra Smith, M.S., E.I.T.

Sierra joined WSE as a junior hydraulic engineer in the fall of 2023 and is excited to apply her knowledge and skills to hydraulic and sediment related challenges in the Pacific Northwest and beyond.

Kristina Roller, M.E., E.I.T.

Kristina joined WSE in the spring of 2025 as a junior hydraulic engineer. Kristina completed her Bachelor's in Civil and Environmental Engineering with an emphasis in Hydraulics and her Master’s in Hydrology and Water Resources within Civil and Environmental Engineering at Utah State University.