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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