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Addressing Maryland’s Sediment Impairments. Lee Currey TMDL Program Non-tidal and Watershed Modeling Division September 11, 2014. Acknowledgments. EPA Chesapeake Bay Program EPA Region III ICPRB MD Department of Natural Resources University of Maryland USGS Versar, Inc

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Addressing maryland s sediment impairments

Addressing Maryland’s Sediment Impairments

Lee Currey

TMDL Program

Non-tidal and Watershed Modeling Division

September 11, 2014


  • EPA Chesapeake Bay Program

  • EPA Region III


  • MD Department of Natural Resources

  • University of Maryland

  • USGS

  • Versar, Inc

  • Virginia Institute of Marine Sciences


  • Listing Methodologies

  • 303(d) Sediment Listings

  • Identifying a Sediment Stressor

  • Sediment TMDL Approach

  • Current Project Status

  • Outstanding Issues

Listing methodologies for solids
Listing Methodologies for Solids

  • Water Clarity

    • Turbidity [COMAR]

    • May not exceed levels detrimental to aquatic life

    • May not exceed 150 units at any time or 50 units as a monthly average

  • Narrative Water Quality Criteria

    • “…State’s waters must be sufficient quality to provide for the protection of and propagation of a balanced population of shellfish, fish and wildlife and allow for recreational activities…” [COMAR]

      (i.e. fishable/swimmable)

History of maryland sediment impairments
History of Maryland Sediment Impairments

  • Existing water quality inventory [303(d) list] identified 97 listings for sediment

  • Many watersheds assessed based on land use and likelihood of sediment impairment

  • Currently no distinction between “suspended sediment” and “sedimentation”

What is a clean sediment impairment
What is a “Clean” Sediment Impairment?

Basin erosion

Channel/Bank erosion


Increased suspended sediments

Substrate homogeneity

Current homogeneity


Interruption in feeding mechanisms

Decreased habitat



Shift in biological community (biocriteria)

Identifying a sediment stressor
Identifying a Sediment Stressor

  • Endpoint – Maryland Biocriteria

  • Stressor – Sediment Related Physical Habitat Parameters

  • Linkage – Statistical Model

Mbss and biocriteria
MBSS and Biocriteria

  • Stratified random sampling of first to fourth order stream (fourth in round 2)

  • Index of biotic integrity

    • Biological condition indicator developed for the fish and benthic communities

    • Multi-metric - aggregates multiple characteristics of biological assemblage

    • Established from regional reference conditions

  • Biocriteria is EPA approved

    • For evaluating biological data for CWA requirements

Mbss monitoring
MBSS Monitoring

Round 2: Approx 10 stations per

8-digit basin

Identifying surrogate sediment parameters
Identifying Surrogate Sediment Parameters

  • Variables that best represent the presence or effects of sediment

    • Combined physical habitat

    • Riparian and upland zone

    • Streambed

    • Channel features

    • Water column

  • 27 variables identified from total MBSS set

  • Reviewed by advisory committee

  • Identifying surrogate sediment parameters1
    Identifying Surrogate Sediment Parameters

    • Further refinement of surrogate parameters:

      • Available for both rounds of MBSS sampling

      • Expected to have discriminatory power and thus not be limited in range of recorded values

      • Not confounded by stream size or other critical natural variables

      • Not completely redundant

    Parameters used in analysis

    Surrogate Variables



    Relationship to Sediment

    Riffle/Run Quality

    Depth, complexity, and functional importance of riffle/run habitat

    0 to 20

    High scors indicate lack of sediment deposition.

    Bank stability

    Composite score.

    Presence or absence of riparian vegetation

    quantitative measures of erosion extent and erosion severity.

    0 to 100

    High scores indicate lack of channel erosion

    Riparian buffer width

    Width of vegetated (i.e., grass, shrubs, or trees) riparian buffer

    0 to 50

    Indirectly related to sedimentation as buffers remove sediment in runoff and protect banks from erosion.

    Instream habitat

    Perceived value of instream habitat to the fish community, including multiple habitat types, varied particle sizes, and uneven stream bottom.

    0 to 20

    High socres indicate lack of sediment deposition.

    Epifaunal Substrate

    Visual rating based on the amount and variety of hard, stable substrates usable by benthic macroinvertebrates.

    0 to 20

    High scores indicate lack of sediment deposition.


    Percentage of gravel, cobble, and boulder particles in the streambed that are surrounded by fine sediment.

    0 to 100

    Direct evidence of sediment deposition.

    Parameters Used in Analysis

    Non sediment stressors
    Non-Sediment Stressors

    • MBSS sites with stressors not related to sediment

      • Acidification

        • ANC < 200 μeq/l and DOC < 8 mg/l (excluding natural blackwater)

      • Urbanization

        • Urban land use > 10%

        • Cl > 50 mg/l

      • Low dissolved oxygen

        • Not removed due to instantaneous sampling methodology

    Parameter selection


    Parameter 1

    Parameter 2

    Parameter 3

    Parameter 4


    Riffle run

    Riparian width




    Riparian width

    Instream habitat


    Epifaunal substrate


    Riffle run

    Riparian width

    Instream habitat



    Riffle run

    Riparian width

    Instream habitat


    Parameter Selection

    • Select most parsimonious model

    • Objective is change in Chi square value

    Model validation
    Model Validation



    * Inconclusive based on 90% confidence interval

    Watershed evaluation for sediment impairment
    Watershed Evaluation for Sediment Impairment

    • Estimate likelihood of sediment impairment at appropriate management scale

    • MDE currently lists sediment impairment at the MD 8-digit scale

    • Average likelihood of sediment impairment per watershed

    Evaluation of model at watershed scale
    Evaluation of Model at Watershed Scale

    Surrogate Sediment Parameters



    1. Min sample>=5

    Tmdl approach reference watershed
    TMDL Approach – Reference Watershed

    Statewide Analysis

    MD 8-digit management scale



    (similar to

    Preston, 2002)



    Likelihood of

    Sediment Impairment

    Target Load

    Watershed clustering
    Watershed Clustering

    • Reviewed previous results from USGS (Preston, 2000)

    • Updated cluster analysis based on new data and focused on sediment

    • Two stage clustering

      • hydrological and geological information

        • Rainfall erosivity (R)

        • soil erodibility (K)

        • watershed slope

      • Land use

    Cbp phase v
    CBP Phase V

    • Interstate coordination

    • MD 8-digit watershed scale

    Sediment loads
    Sediment Loads


    *Preliminary CBP Phase V Loads

    Addressing 303 d listings
    Addressing 303(d) Listings

    • WQA

      • Determined from likelihood of sediment impairment

      • Inferential statistics used to address borderline cases

    • TMDL

      • Reference watersheds

      • Watershed model scenarios

      • Limits of implementation

      • Maximum practical reductions

    Where are we now
    Where are we now?

    • Independent review of logistic regression model

    • Working on two stage clusters

      • talking with USGS about best cluster methods for reference watersheds

    • Coordinating with CBP (USGS and ICPRB) on Phase V sediment calibration

    Outstanding issues
    Outstanding Issues

    • Normalizing loads

    • Scale of impairment

    • Sediment loads for reference conditions

    • Point sources

    • MS4 permits

    Thanks questions and comments
    Thanks !Questions and Comments