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Evaluating the Effectiveness of Stream Restoration in Maryland: Integrating
Existing and New Data from Restoration Monitoring
Chesapeake Bay Trust Forum, June 2019
Solange Filoso
Research Questions
1. How does effectiveness of stream restoration at reducing nutrient and sediment loads vary among different projects implemented in MD?
2. What factors influence project performance?
Potential factors influencing restoration performance
• Stream position in watershed
• Watershed imperviousness
• Catchment size (area)
• Restoration design
• Magnitude of discharge
• Loading concentrations, dominant species of N and P
• Catchment topography, channel slope
Objectives
• To use pre- and post-restoration data from a number of streams in MD monitored with compatible methodology to determine changes in nutrient and sediment loads.
• Calculate effectiveness in terms of removal rates (kg/ha/yr) and relative removal (% of load in pre-restoration stream/site).
• Examine potential factors influencing project performance.
Study StreamsStream
Drainage
area (ha)
Impervious
ness (%)
Position in
watershedWatershed
Physiographic
region
New Data
Collected
Dividing Cr. 89 32 Lowland Magothy Coastal Plain YES
Cabin Br.
(Saltworks)49 55 Lowland Severn Coastal Plain YES
Church Cr. 227 56 Lowland South Coastal Plain YES
Cypress Cr. 143 46 Lowland Magothy Coastal Plain YES
Howard’s Br. 96 11 Lowland Severn Coastal Plain NO
Wilelinor 106 48 Lowland South Coastal Plain NO
Linnean 13 27 Headwater Rock Cr. Piedmont NO
Park Drive 1.3 18 Headwater Anacostia Coastal Plain NO
Clements Cr.
(C. Hills)6 15 Headwater Severn Coastal Plain NO
Red Hill Br. 18 - Headwater Patuxent Coastal Plain NO
Streams monitored
for this project
Streams with
monitoring data
available
Monitoring Designs
Control = Before
Before-After restoration
Control = Above
Above-Below restoration
Paired-catchments
Control = Similar catchment
Before/After/Control/Impact (BACI)
Control = Similar catchment before and after
Above-Below, Before-After restoration
Methods used for data collection: Rain, discharge and water quality
Measuring rain and discharge
Water sampling
Important monitoring attributes
• Data were collected for at least 1 year before and 1 year after restoration.
• Data were collected during base flow and stormflow conditions.
• Base flow samples were collected monthly to quarterly.
• Stormflow samples were collected for at least 8 storm events per year in each site.
• Rain depths and stream flow were recorded continuously.
• Rain data were collected on site for each catchment.
Restored streams were effective at reducing most pollutant loads but reductions varied
LOAD
INCREASED
LOAD
DECREASED
-100
-50
0
50
100
% C
hange
% Change in pollutant loads with restoration
TSS TN TP
Effectiveness of headwater channels was higher than of lowland channels
76 to
91%
0 to
49%
36 to
82%
0 to
34%
TSS TN TP
51 to
76%
0%
Effectiveness was correlated with catchment size
% L
oa
d r
ed
uctio
n
Catchment size (hectares)
Effectiveness decreased with increased imperviousness in catchment
% L
oad
re
du
ctio
n
% imperviousness
Stormflow was a dominant component of annual discharge in smaller and more impervious catchments
0
50
100
PARK DR. C HILLS LINNEAN RED HILL WIL SALT HB DIVIDING CYPRESS CHURCH
%
Base Flow Stormflow
0
50
100
PARK DR. C HILLS LINNEAN RED HILL WIL SALT HB DIVIDING CYPRESS CHURCH
%
Base flow Stormflow
CONTROL/PRE-
RESTORED/POST-
Stormflow concentrations decreased substantially in headwater channels
HEADWATERS LOWLANDS
CTRL
REST
HEADWATERS LOWLANDS
HEADWATERS LOWLANDS
CTRL
REST
HEADWATERS LOWLANDS
CTRL
REST
HEADWATERS LOWLANDS HEADWATERS LOWLANDS
Concentr
atio
n (
mg/L
)F
WM
Concentr
atio
n (
mg/L
)
Restored stream capacity to reduce loads in stormflow tend to decrease with rain size
Example from a lowland channelExample from a headwater channel
Rain events > 1 in were rare but contributed to ~ half of the total annual rain in catchments
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8/7
/11
9/2
/11
9/2
8/1
11
0/2
4/1
11
1/1
9/1
11
2/1
5/1
11
/10
/12
2/5
/12
3/2
/12
3/2
8/1
24
/23
/12
5/1
9/1
26
/14
/12
7/1
0/1
28
/5/1
28
/31
/12
9/2
6/1
21
0/2
2/1
21
1/1
7/1
21
2/1
3/1
21
/8/1
32
/3/1
33
/1/1
33
/27
/13
4/2
2/1
35
/18
/13
6/1
3/1
37
/9/1
38
/4/1
38
/30
/13
9/2
5/1
31
0/2
1/1
31
1/1
6/1
31
2/1
2/1
31
/7/1
42
/2/1
42
/28
/14
3/2
6/1
44
/21
/14
5/1
7/1
46
/12
/14
7/8
/14
8/3
/14
8/2
9/1
49
/24
/14
10/2
0/1
41
1/1
5/1
41
2/1
1/1
41
2/2
8/2
01
41
/23
/201
52
/18
/201
53
/16
/201
54
/11
/201
55
/7/2
015
11/7
/201
61
2/3
/201
61
2/2
9/2
01
61
/24
/201
72
/19
/201
73
/17
/201
74
/12
/201
75
/8/2
017
6/3
/20
17
6/2
9/2
01
77
/25
/201
78
/20
/201
79
/15
/201
71
0/1
1/2
01
71
1/6
/201
71
2/2
/201
71
2/2
8/2
01
7
Daily rain
2011 2012 2013 2014 2015 2016 2017
RAIN SIZE FREQUENCY CONTRIBUTION TO TOTAL VOLUME
Rain
depth
(in
)
Summary
1. 80-90% of the restored streams examined reduced TSS and TN loads,
but only 40% reduced TP loads.
2. Load reduction was relatively higher in headwater channels.
3. Project performance was associated with stream position in watershed,
% imperviousness, and size of catchment.
4. Stormflow contributed most of the annual discharge in headwater
streams; in lowland channels base flow was important as well.
5. Performance of headwater channels was based on their capacity to
reduce loads in stormflow.
6. Performance of lowland channels was based on their capacity to reduce
loads in both base flow and stormflow.
Final Remarks
1. Despite inferior performance of lowland channels, they can
potentially reduce large loads given their size.
2. Trade-offs associated with lowland channels should be
carefully considered.
3. Other factors are likely to influence restoration performance.
4. Synthesis and evaluation of monitoring data is essential to
improve our capacity to predict the outcomes of restoration
projects as well as to develop more cost-effective monitoring
strategies.
Acknowledgments
FilosoTranslation Slides
What does this mean for me? • The efficacy of stream restoration at reducing nutrient and
sediment loads varies among projects.
• Upland streams restored with RCS are generally more effective than valley channels.
• TN, TP, and TSS were consistently reduced in upland systems, while only TN and TSS were reduced in valley systems, but at lower rates.
• Efficacy is associated with the capacity of streams to retain nutrients and sediments during a wide range of storm sizes.
• Restoration improves retention in upland projects during small and large storms, but ONLY in smaller storms in valley channel projects.
• The frequency of storms > 1 inch was only 9% during the monitoring period but they contributed almost 50% of the total rain volume.
What does this mean for me? What do I take from this if I am a practitioner? • Implement projects in headwater areas where feasible to
maximize nutrient/sediment reductions.
What do I take from this if I am a regulator?• Consider site location as an important factor when
reviewing potential projects.
• Upland stormwater best management practices and upland stream restorations may decrease the effect of high flows on downstream areas (e.g. 2018).