Urban Hydrology and Water Quality

What We Can Do:

Surface water management programs increasingly call for an integrated approach to flood control, water quality, channel stability, and aquatic resource protection. Whether the challenge is at the site or watershed scale, NHC brings a comprehensive approach and state-of-the-art tools to support policy development, planning, and design to protect and enhance the aquatic environment.

Derek Stuart
Brent Wolfe
British Columbia:
Barry Chilibeck
Ken Zhao
Ed Wallace
Gilles Rivard
Asia and Africa:
Mike Okun
Latin America:
Guilherme deLima

NHC develops and applies state-of-the-art hydrologic, water quality, and stormwater runoff models combined with advanced statistical analyses to address drainage, water quality, and aquatic resource issues. Our expertise in a wide array of surface water modeling software allows us to select and match appropriate technical tools to the scale and complexity of each client's problem. We combine these technical abilities with specialized regional experience in compliance with regional, state, and national regulatory requirements.

NHC provides integrated hydrologic and water quality planning and design services for management of stormwater runoff in urban, agricultural, and wildland settings. Our services include:

  • Hydrologic Modeling and Assessment
    Delivered at project, catchment, and watershed scales.
  • Basin Planning
    To meet ecological, flood control, and water quality objectives.
  • Development
    Hydro-modification guidelines, water quality design criteria, and analysis methods.
  • Pollutant Load and Transport Modeling
    To evaluate options to most efficiently and effectively meet regulatory requirements.
  • Stormwater BMP Design
    Including low impact development/green stormwater infrastructure.
  • Hydraulic Analysis
    Examining separated and combined collection systems for conveyance, inflow and infiltration, and combined sewer overflow control studies.
  • Urban Stream Restoration
    Designing urban stream restoration and conduit daylighting to enhance aquatic habitat, community open space, water quality, and stream stability.


NHC has over 30 years of experience working with both private and public organizations in planning, designing, and implementing urban hydrology and water quality projects.

  • Stormwater Modeling and Analysis
    Using a range of simple to sophisticated applications of stormwater modeling tools such as BASINS, HSPF, SWMM, WARMF, NSPECT, INFOWORKS, and others. NHC has also developed customized regional tools to support watershed initiatives and regional planning, such as the Pollutant Load Reduction Model (PLRM) for the Lake Tahoe Basin. Our tools facilitate sophisticated and regionally consistent analysis for broad groups of users by automating access to pre-processed technical data such as spatial variations in precipitation, soils, and water quality characteristics.
  • Water Quality Watershed Assessment
    Applied screening and planning level models using GIS-based assessments to estimate pollutant loads and investigate potential structural and non-structural watershed management actions for improvement of water quality. These investigations cover a wide range of hydrologic environments (e.g., tropical Oahu, Puget Sound, alpine Lake Tahoe, and the Mojave Desert), and an equally wide range of water quality problems and objectives.
  • TMDL Planning and Implementation Support
    Using customized tools and models, NHC has accurately characterized baseline conditions and formulated program strategies for local and regional governments to cost-effectively meet TMDL (Total Maximum Daily Load) targets. We have developed program priorities, cost estimates, and approaches that integrate capital improvements with maintenance and operational plans for improved water quality.
  • Stormwater Guidelines
    Assisting local and state agencies to develop stormwater policies, monitoring protocols, continuous hydrologic modeling methods for hydro-modification analyses, standard details for BMP (Best Management Practices) implementation, and simplified sizing criteria for BMPs that ensures long-term effectiveness in pollutant load reduction.

Stream incision due to
hydro-modification, Puget Sound

Pollutant load model user's manual, TMDL support, Lake Tahoe

Flood basin conversion to
wetland and open space,
San Bernardino County, CA

Benefits & Results:

  • Our sound technical analysis and an understanding of physical, biological, and community objectives produce cost-effective solutions to stormwater and urban runoff problems.
  • Conveyance, water quality, stream geomorphology, and aquatic resource objectives are all effectively integrated into our projects and programs.
  • We help develop feasible goals and provide practical solutions to achieve positive environmental gains.