Four Mile Run Levee Corridor Stream Restoration 30% Design Summary U.S. Army Corps of Engineers, Baltimore District
Presentation Outline Four Mile Run 1.) Historic Perspective 2.) Existing Conditions 3.) Objectives 4.) Field Work 5.) Fluvial Geomorphic Design 6.) Proposed Solution U.S. Army Corps of Engineers, Baltimore District
Historic Perspective Four Mile Run pre-1885
Historic Perspective Four Mile Run circa 1909 Wetlands Additional railroad tracks
Historic Perspective Four Mile Run circa 1945
Historic Perspective Four Mile Run levee (1978/2004) D/S West Glebe Road
Four Mile Run today Existing Conditions STRESSORS Bridges/Infrastructure Development Increased imperviousness RESULTS Habitat loss Excessive nutrients Sedimentation Flooding Impaired water quality
Existing Conditions Four Mile Run today West Glebe Road bridge conveyance problems
Existing Conditions Stream Segment 1 Transition area (tidal and non-tidal) Downstream of Long Branch downstream of Mount Vernon Avenue bridge Approximate length = 1800 feet
Existing Conditions Stream Segment 1 Mudflats at low tide Excessive sedimentation caused by lack of defined channel, tidal influence and improper sediment maintenance
Existing Conditions Stream Segment 2 Downstream of West Glebe Road Downstream of Long Branch confluence Approximate length = 2200 feet
Existing Conditions Stream Segment 2 Drop in streambed elevation Damaged gabion mattresses (sediment rubbing) Suspended sediment on top of the gabions
Existing Conditions Stream Segment 2 Outfall on right bank upstream of West Glebe Road More than 4 feet of downcutting since levee construction Saprolite feature that has become exposed
Existing Conditions Stream Segment 2 West Glebe Road bridge
Existing Conditions Stream Segment 3 Downstream of I-395 Upstream of West Glebe Road Approximate length = 1350 feet
Existing Conditions Stream Segment 3 West Glebe Road bridge Upstream view of conveyance problems I-395 bridge Remnants of an old bridge structure and sheet piling under the right bridge span
Existing Conditions Stream Segment 4 Approximately 500 ft upstream of Shirlington Road Upstream of I-395 Approximate length = 1250 feet
Existing Conditions Stream Segment 4 Looking downstream at I-395 bridge Stream invert is much lower in right span of the bridge Sunfish spawning areas
Existing Conditions Stream Segment 4 Fish blockages Streambed degradation upstream of Shirlington Road
Existing Conditions Long Branch Sediment deposition under the South Glebe Road bridge Exposed sewer line downstream of the South Glebe Road bridge
Existing Conditions Long Branch Check dam/ grade control
Existing Conditions Summary of Problems Bridges! Gabion baskets Development/Outfalls Lack of floodplain Sediment Instability Trash Lack of vegetated buffer Fish blockage Positive Impacts on Four Mile Run Municipalities sewer maintenance
Engineering Objectives Maintain flood protection Improve conveyance through structures crossing the stream reduce back eddies and erosion Increase stability of the stream system Provide self-sustaining geomorphic conditions to reduce/eliminate channel maintenance Remove fish blockages Establish smooth transition from alluvial system into tidal environment Improve aquatic habitat Improve visual values
Field Work July/August 2006
Fluvial Geomorphology Channel slope Width Depth Discharge Velocity Roughness of channel materials Sediment size (Leopold et al., 1964)
Fluvial Geomorphology Further Classification
Fluvial Geomorphology Valley Types Valley Type I II III IV V VI VII VIII IX X Description V notched canyons, rejuvenated sideslopes Moderately steep, gentle sloping side slopes often in colluvial valleys Alluvial fans and debris cones Gentle gradient canyons, gorges and confined alluvial valleys Moderately steep valley slopes, U shaped glacial trough valleys Moderately steep, fault controlled valleys Steep, highly dissected fluvial slopes Wide, gentle valley slope with a well developed floodplain adjacent to river terraces Broad, moderate to gentle slopes, associated with glacial outwash and/or eolian sand dunes Very broad and gentle slopes, associated with extensive floodplains Great Plains, semi-desert and desert provinces; coastal plains and tundra; Lacustrine valleys Stream Types A and G B A, G, D and B F and C D, C and Bc B, G and C A and G C, E and Bc Predominantly D and some C C and D
Fluvial Geomorphic Approach Priority 1 for an incised stream From Doll et al., 2003 Establish bankfull stage at historic floodplain elevation
Fluvial Geomorphic Approach Priority 2 for an incised stream From Doll et al., 2003 Create a new floodplain and stream pattern with streambed remaining at present elevation
Fluvial Geomorphic Approach Priority 3 for an incised stream From Doll et al., 2003 Widen floodplain at existing bankfull elevation
Fluvial Geomorphic Approach Option for a stream system that has not downcut to the point of becoming incised Four Mile Run Combination of techniques Raise streambed to provide floodplain access where possible or create benches at the appropriate elevation by cutting into the floodplain terrace
Fluvial Geomorphic Structures Cross-vane
Fluvial Geomorphic Structures J-hook
Fluvial Geomorphic Structures W-weir
Proposed Solutions Stream Segment 1
Proposed Solutions Stream Segments 1 & 2
Proposed Solutions Stream Segments 2 & 3
Proposed Solutions Stream Segment 3
Proposed Solutions Stream Segment 4
Conclusions * Improve conveyance through stream crossings, decreasing local flooding * Proposed cross-vane, J-hook and W-weir structures, in combination with proper stream geometry and profile will create a stable, healthy, functional stream system.
Thank you. Any questions?