Natural Agents of Watershed ChangeFloods The San Antonio River and Guadalupe River converge during a flood.
Natural Agents of Watershed ChangeDrought Brummetts Creek in southern Indiana following 8 weeks without measurable rain.
Natural Agents of Watershed ChangeErosion and Sediment Deposition How much is natural??
Timber Harvesting • Sediment production from logging roads is 770-fold higher than unlogged forests • 30% due to surface erosion • 70% due to mass soil failure
Agricultural Impacts • Channelization • Drainage tiles • Removal of riparian vegetation • Tillage practices • Nutrient loss • Soil loss
Indiana Drainage Code • Enacted by state legislature in 1965 • Co. Drainage Boards and Co. Surveys have authority • Must ‘maintain’ regulated drains in county • Code specifies that all vegetation may be removed for proper operation of the drain
Legal Drain Cleaning ‘Uncleaned’ ‘Cleaned’
IBI and Habitat Score vs. % Forest Land Cover From: Wang et al. 1997, for 134 sites on 103 WI streams
IBI scores vs. Four Categories of Land Use. Correlations with agriculture and forest were statistically significant. From: Roth et al. 1996 in Michigan watershed – at 23 1st – 3rd order stream sites
Potential Downstream Influences on Upstream Communities From: Pringle, 1997)
The Problem: Sediment Deposition • Human disturbance causes sediment deposition in streams • Habitat degraded • Decline in biotic integrity of stream • Restoration needed
David Starr Jordan(IU President: 1885-1891) • Earliest published comment on the destructive effects of sediments in streams (1889) • Wrote about loss of trout habitat in Colorado due to mining
The Effects of Sedimentation • Habitat • substrate for plants • loss of benthic habitats • Macroinvertebrates • (60%< if TSS >120 mg/L over norm – Gammon, 1970) • interference with respiration • gilled macroinvertebrates • smothering • loss of interstitial space
The Effects of Sedimentation Fishes • interference with respiration • gill clogging • 53-77% > in O2 consumption • loss of rearing habitat • emergence • visual impairments for feeding • move downstream to avoid sluicing (4.3 km)
Moving Sediment DownstreamFlushing Flows • Regulated Streams (dams) • General Uses • One time sediment release • Regular maintenance of regulated streams • Benefits • Flushing out fines • Channel maintenance • Riparian habitat maintenance
Glen Canyon Dam Controlled Release of 1996 • Max Q with dam = 34,000cfs • Ave. peak flow w/o dam = 93,400 cfs • Released 45,000 cfs for 7 days
DNR Dam Release • May 18, 1998 - Sluicing Event • Increased sediment flow • Anoxic pulse
The Fawn River * measured 6 days after a discharge event
Greenfield Mills - before Greenfield Mills - after
Fish Data • No live fish observed 5/19/98 • 27 dead fish observed at Rock Dam in 30 minutes • Dead fish had blackened gills • all adult fish
Options For Restoration and Enhancement • Options for sediment removal. • Moving sedimentsdownstream • Remove them from the system
Moving Sediments Downstream • Natural flow fluctuation • Flushing flows • Habitat alteration (In-stream structures)
Moving Sediment Downstream:Natural Flow Fluctuation • Unregulated streams • After temporary discharge • Example:Valley Creek, Minnesota (Waters 1992) • Deposition decimated trout and invertebrates • 2 years of natural flow variation eventually cleaned bed • Trout and invertebrates recovered
Moving Sediment DownstreamFlushing Flows • What flow regime to use? • How big (magnitude)? • How long (duration)? • When (timing)? • Comprehensive summary of techniques: Reiser et al (1985) for the Pacific Gas and Electric Co.
Moving Sediment DownstreamFlushing Flows Magnitude • Three primary approaches • Hydrological • Use runoff records (200% mean annual Q) • Morphological • Use channel characteristics (1.5 year flood) • Sedimentological • Based on sediment transport equations
Moving Sediment DownstreamFlushing Flows • Timing • Fish and wildlife requirements • Spawning: biological cue, floodplain spawners • Rearing: juveniles in the floodplain • Riparian vegetation • Historical runoff period • Water availability
Moving Sediment DownstreamFlushing Flows Considerations • Downstream effects • Sediments downstream • Disturbance of spawning gravel • Speed of flow release and recession • Quality of flush water • *Most successful in high gradient and riffles*
Moving Sediment DownstreamIn-stream Structures • Most tested techniques • Used commonly for trout • Macroinvertebrates & other organisms benefit • Localized scouring • Goals for use of in-stream structures • Speed current and increase turbulence • Deepen channel • Increase substrate particle size
Moving Sediment DownstreamIn-stream Structures • Techniques for localized scouring • Placement of roughness elements in stream • Wing deflectors • Temporary structures
Moving Sediment DownstreamIn-stream Structures • Roughness elements • Boulders, stones and logs • Increase scour • Turbulence • Velocity • Habitat creation
Moving Sediment DownstreamIn-stream Structures • Wing Deflectors • Triangular, embedded in bank, angled downstream • Narrow and deepen stream • Increase velocity and scouring