8: FLUVIAL GEOMORPHOLOGY OF THE UPPER ESOPUS CREEK WATERSHED AND IMPLICATIONS FOR STREAM MANAGEMENT
Dan Davis
Mark Vian
Stream Management Program
New York City Department of Environmental Protection
71 Smith Avenue, Kingston, NY 12401
Peter L.K. Knuepfer
Department of Geological Sciences and Environmental Studies
Binghamton University, Binghamton, NY 13902-6000
Nicolas Miller
Binghamton University and Field Geology Services
P.O. Box 985, Farmington, ME 04938
INTRODUCTION
The New York City water supply system depends on the maintenance of natural high water quality in the watersheds that drain into the reservoirs that store water for the system. Accordingly, concentrations of suspended sediment in both streams and reservoirs are major concerns, and the identification and remediation of sites that are concentrated sources of high suspended load/turbidity are essential to water quality management.
The concern about water quality by New York City's Department of Environmental Protection (DEP) is further motivated by a Filtration Avoidance Determination (FAD), which was renewed by the U.S. Environmental Protection Agency in 2007 and currently runs through 2017. This determination allows New York City to avoid the high capital cost that would be associated with building and maintaining a filtration system to treat the New York City water supply originating west of the Hudson River (∼90% of the total supply). The FAD requires DEP to maintain high water quality through, among other practices, the development of stream management protocols and funding additional stream restoration projects (US EPA, 2007).
The DEP established a Stream Management Program to oversee the assessment of stream corridor condition and the development of management strategies for the watersheds that comprise the West-of-Hudson water supply system (Figure 1), including the Ashokan Reservoir/Upper Esopus Creek watershed (Figure 2). The DEP has worked with municipal, county, state and federal partners to develop Stream Management Plans (SMP) for many of the principal streams supplying the Ashokan, Schoharie, Cannonsville, and Pepacton Reservoirs. The work in the Upper Esopus Creek watershed that will be summarized in this field trip has been part of this overall effort (see www.catskillstreams.org).
The purpose of this field trip, then, is to explore the Upper Esopus Creek watershed, highlighting historic changes to the creek channel (Miller, 2009) and strategies that have been implemented or are being considered to alleviate or manage suspended sediment yield. We will examine sites where lateral migration or change in base elevation of the channel is degrading water quality or threatening property damage, where bank erosion has created a source of turbidity, and where stream restoration/remediation strategies have been applied and will be applied in the future in efforts to remediate "hotspots" of erosion and sources of high suspended sediment loading.

8: FLUVIAL GEOMORPHOLOGY OF THE UPPER ESOPUS CREEK WATERSHED AND IMPLICATIONS FOR STREAM MANAGEMENT

Cross Wallkill River, incised into Ordovician shales and siltstones

Cross Rondout Creek, also incised into Ordovician shales.
Lefever Falls on the left.

Cross Esopus Creek

Kings Town Stone Quarry on right into Middle Devonian Mt. Marion Formation.

Kenozia Lake on right.
Drained in 2008 for repairs, the lake has refilled quickly in 2009 due to the heavy spring melt off and rains.

Weir that divides West and East basins of Ashokan Reservoir.

STOP 1. Ashokan Reservoir and Esopus Creek Watershed.
Ashokan Reservoir was the first of the New York City water-­supply reservoirs to be constructed in the Catskills. The dam across Esopus Creek was completed in 1913 and the reservoir was impounded by 1914 (Schneiderman, 2000; New York City Department of Environmental Protection, 2009). Water is carried to New York City through the Catskill Aqueduct, completed in 1915. Because of concerns about the influx of suspended sediment from Esopus Creek, the reservoir is managed in two basins. The West Basin receives input from Esopus Creek (and the Shandaken Tunnel from Schoharie Reservoir), and is designed to act as a settling basin. It is separated from the East Basin, from which water is withdrawn into the Catskill Aqueduct, by the weir across which we have just driven (Figure 9). This overview provides a dramatic view into the mountainous upper Esopus Creek watershed. Also, an automated suspended sediment sampling site is located just east of the weir, visible from this overview site.

Descend into Esopus Creek valley bottom.

Bridge across Esopus Creek
Stony Clove enters from left just downstream (right) of bridge. Stony Clove is a significant source of suspended sediment load/turbidity during high flow events and will be the location of Stops 6 and 7.

STOP 2. Esopus Creek at Woodland Valley Restoration Demonstration Site.
This stop in Esopus Creek Reach 7 will provide an introduction to the challenges in stream management of the Esopus Creek watershed and an illustration of the application of channel stabilization/stream restoration techniques. There is an informational kiosk at the site documenting the project history. The site is at the confluence of Woodland Creek with Esopus Creek – a setting that is inherently dynamic given the variability in magnitude of water and sediment discharge from the two mountain streams (Figure 10). Anecdotal and aerial photo evidence suggests that the channel and bar formation have undergone dramatic shifts in response to large flood events. The setting's inherent "instability" is compounded by a double-span bridge located just downstream of the confluence that produces a clear constriction in channel dimensions. Following the January 1996 flood, a head-cut into underlying glacial lake clay propagated through a secondary channel along the left bank and eventually captured most of the Esopus Creek flow (Figure 10). The altered alignment of the channel, the stratified composition of the 32 foot (9.8 meter) high terrace (from bottom to top: glacial lake clay, glacial till, prehistoric stream deposits; Figure 11) and subsequent floods resulted in a rapidly retreating eroding bank (approximately 3 feet or 0.9 m per year).
Risks associated with continuing erosion included increasing potential for exhuming several residential septic systems, causing additional property damage, producing a continuing source of turbidity and creating a hazard to recreational users of the stream (Figures 10 and 11).
In 2000, DEP hired FIScH Engineering (principal engineer Dr. Craig Fischenich) to complete an assessment and conceptual design for remediating this reach (Fischenich, 2001). The hydraulic and stability analyses, sediment transport calculations, and geomorphic assessment resulted in recommendations for an approach that incorporated several technical techniques including a channel relocation based upon natural channel design principles, bioengineering and traditional bank revetment, and habitat and recreational enhancement features. DEP selected this project to be the demonstration stream restoration project for Esopus Creek required by the US EPA as part of the FAD schedule of compliance (US EPA, 2007). The project was constructed in 2003 in two stages: the channel work, bank revetment, and flood plain reconstruction were completed by Oct. 1, 2003 and the vegetation (trees and willow fascines) and bioengineering (VRSS) were completed in early Dec., 2003. Figure 12 is an aerial view of the site taken approximately one year after construction (Aug., 2004).

Office of Ashokan Watershed Stream Management Program on left
(which will be lunch stop)

Bridge across Broadstreet Hollow (location of Stops 5a and 5b)

Shandaken Tunnel (location of Stop 4b) emerges on right side of highway

Esopus Creek bridge

Start of bridge across Birch Creek

STOP 3. Esopus Creek Bank Failure on Reach 16.
Note: This is Private Property. Get permission from owner across road before crossing property to creek.
Esopus Creek has been actively changing its channel configuration through an anabranching reach from near Hatchery Hollow about 3 km upstream from this site. This has included a number of avulsions and meander-bend migrations (Miller, 2009). At this site, a very tight meander bend has been expanding westward at least since 1959 (Figure 13). This expansion has resulted in undermining and rapid headward growth of propagating failures in an elevated terrace that forms the left descending stream bank. Fluvial gravels overlie interbedded glacio-lacustrine clays and silts and glacial till. Stormwater runoff and groundwater flow off the adjacent mountainside has limited infiltration potential due to the impermeable glacial deposits and emerges as springs on the creek bank. Water does infiltrate into rotational slip surfaces in the underlying lacustrine unit resulting in very active collapse of the bank (Figures 14 and 15). This reach is often the upstream source of suspended sediment into Esopus Creek following high water events. This reach is part of DEP's longterm geomorphic monitoring program with 6 monumented cross sections, repeated longitudinal profile surveys, sediment sampling, and GPS-based mapping of channel feature alignment.
Risks associated with continuing erosion included increasing potential for exhuming several residential septic systems, causing additional property damage, producing a continuing source of turbidity and creating a hazard to recreational users of the stream (Figures 10 and 11).
In 2000, DEP hired FIScH Engineering (principal engineer Dr. Craig Fischenich) to complete an assessment and conceptual design for remediating this reach (Fischenich, 2001). The hydraulic and stability analyses, sediment transport calculations, and geomorphic assessment resulted in recommendations for an approach that incorporated several technical techniques including a channel relocation based upon natural channel design principles, bioengineering and traditional bank revetment, and habitat and recreational enhancement features. DEP selected this project to be the demonstration stream restoration project for Esopus Creek required by the US EPA as part of the FAD schedule of compliance (US EPA, 2007). The project was constructed in 2003 in two stages: the channel work, bank revetment, and flood plain reconstruction were completed by Oct. 1, 2003 and the vegetation (trees and willow fascines) and bioengineering (VRSS) were completed in early Dec., 2003. Figure 12 is an aerial view of the site taken approximately one year after construction (Aug., 2004).

Junction Hwy. 42 on left at Shandaken.
The highway climbs up Bushnellsville Creek through Deep Notch and into the Schoharie Creek watershed.

STOP 4A. Esopus Creek Gage at Allaben (Reach 11/12).
A USGS gaging station, maintained in cooperation with the DEP, has been operating at this site since 1988; from 1963 to 1988 a gage was located about 0.8 km upstream. Bankfull discharge is ∼3000 cfs (85 cumecs) has been exceeded numerous times during the period of record, and the site has recorded peak discharges of at least 15,000 cfs (425 cumecs) 4 times.
The estimated 100year flood at this site is around 26000 cfs (∼740 cumecs) (NYCDEP et al., 2007), whereas the largest flood of record — April 2, 2005 — was 21,700 cfs (∼615 cumecs). This site also has been used as a location to measure the hydraulic geometry of the bankfull channel. Miller and Davis (2003) used this as one of their calibration sites in developing regional bankfull discharge and hydraulic geometry curves for the Catskills region.
Realignment of Hwy. 28 in the 1960s was accompanied by cutoff of a natural meander downstream of the bridge (Figure 16; Miller, 2009). Miller (2009) describes the changes in this way: In 1959 the stream bifurcated around a large island (I11-1) upon entering the meander bend. But with road construction and cutoff of this meander, a new island (I11-3) formed just upstream of the old meander bend, as seen on the 1980 aerial photograph (Figure 16). The stream impinged on the road 200 meters farther upstream (20.2 km). By 2001, this island was attached to the left bank and no longer part of the channel. A new island (I11-5) has formed 140 meters farther downstream due to a channel avulsion across the floodplain leaving the old thalweg between the newly formed island I11-5 and the road.

STOP 4B. Shandaken Tunnel Portal.
The Shandaken Tunnel brings water from Schoharie Reservoir to Esopus Creek to contribute to the New York City water supply system. This 18­mile (29­km) long underground tunnel, built by hand between 1917 and 1924, was the longest handmade aqueduct in the world when it was completed. Both minimum and maximum discharge from the tunnel as well as turbidity limits are regulated by the New York State Department of Environmental Conservation in order to balance recreational (and ecological) uses of Esopus Creek downstream of the tunnel with water­supply needs of New York City.

STOP 5A. Broadstreet Hollow Restoration Project: Reference Reach.
Severe flooding in 1996 resulted in destabilization of a section of the right bank of the Broadstreet Hollow stream, with bank widening that threatened some houses on the left bank. An emergency response team relocated the channel and used extensive rock riprap to harden the banks and stream bed, but in doing so further destabilized the channel (Greene County Soil and Water Conservation District, 2008). Rapid incision of the channel into underlying glacial lake sediment was exacerbated by a high flow in 1999, resulting in destabilization of the left bank and development of a migrating artesian mud boil within the channel. This produced high turbidity levels, with Broadstreet Hollow becoming a significant source of turbidity for Esopus Creek. By 2000, the Broadstreet Hollow Restoration Project was initiated cooperatively among the Greene County and Ulster County Soil and Water Conservation Districts and the DEP Stream Management Program. The project was designed according to Natural Channel Design guidelines, using a reference reach upstream of the project area to define "natural" step-pool conditions and a construction program that attempted to recreate such conditions in the project reach.
The Broadstreet Hollow creek here displays a typical step-pool pattern with large cobble and boulder bed load. This reach is classified as a Rosgen B3 channel (Rosgen, 1996). Sediment size and distribution as well as channel morphology (hydraulic geometry and slope) provide the targets for design of the restoration reach using Rosgen's natural channel design methodology. This site also has been monitored since project initiation; repeated crosssection measurements have been coupled with monitoring transport of large marked boulders to document changes in this "natural" channel reach.

STOP 5B. Broadstreet Hollow Restoration Site: Restoration Reach.
Complex glacio-lacustrine and post­glacial geology along with residential development have contributed to the challenges in restoring and stabilizing this reach of the Broadstreet Hollow stream. As reported by GCSWCD (2008), slumping of glacio-lacustrine clays on the right bank has been fostered by artesian pressure in an interlayered sand deposit that has resulted in an artesian boil within the stream channel. Dewatering wells were installed; they have since been decommissioned. However, mud boils have continued to propagate upstream within the channel, still present in June 2009. Channel restoration was designed using the step-pool bed form and hydraulic geometry of the reference reach. Large quarried rocks were used to construct "cross vanes" to function as boulder-­dominated steps in a constructed B3 channel (Figure 17). Several high flow events through this reach have caused some of the rock structures to be flanked or to need repair. Also, some of the structures have caused excess scour in the pool below the constructed step resulting in impaired fish passage at low flow. Willows and other riparian trees also were planted along the bank to add to bank stabilization.

Left side of road undergoes routine repairs
Left side of road undergoes routine repairs due to collapse of underlying glaciolacustrine clays. Note bedrock exposure across creek.

Bridge over Stony Clove; Stony Clove gaging station.

STOP 6. Lanesville Demonstration Restoration Project Site on Stony Clove Creek.
A long history of channel modification and response has led to severe bank erosion and undermining of the right bank of Stony Clove just downstream of the hamlet of Lanesville. This reach was chosen for remediation because the development of a landslide on the left bank (Figure 18) was a significant source of fine sediment and turbidity into Stony Clove, Esopus Creek, and Ashokan Reservoir. This reach also had become increasingly confined by channel modifications, exacerbating the tendency to undermine the unstable left bank. Bank stabilization was promoted through construction of a bankfull bench at the toe of the slope, designed to re-establish a floodplain and minimize the interaction of most flows with the unstable bank (DuBois, 2003). Natural channel design principles were followed, including the construction of rock vanes and cross vanes within the channel and planting of a riparian buffer along the right bank and on the constructed bench (DuBois, 2003). The project was begun in 2003 but not completed until 2005 because of high water levels in the creek. Since construction this project has received several flow events around or greater than the bankfull discharge and has functioned quite well in stabilizing the reach and reducing turbidity downstream.
OHM 2019: Error in UTM, it should be 560227E not 566227E .

Meteorological station on right.

STOP 7. Landslide Along Stony Clove Creek.
Get permission from landowner before walking down to creek.
The Ashokan Watershed Stream Management Program Action Plan (http://www.catskillstreams.org/majorstreams_ec.html) identifies this reach of the stream between the Silver Hollow Bridge and the Route 214 crossing 1 km downstream as the highest priority restoration target for improving water quality in the Esopus Creek watershed. This area has a long history of modification, including development and construction of a railroad line (Figure 19) and various efforts to control the creek channel alignment. Today there are three distinct streambank/hillslope failures into glacial lake sediment and glacial till that are quite active. During spring snow melt and after rainfall runoff events this reach of stream is the most significant "point source" of turbidity for days and sometimes weeks after high water events (Figures 20 and 21). This stop is located at the largest and most problematic of the failures. It is a large active landslide initiated sometime prior to 1995. Upslope propagation of the slope failure resulted in collapse of a railroad right-of-way as well as increased groundwater and sediment discharge. The scale of this landslide presents especially great challenges for channel restoration and suspended sediment management. We will discuss restoration and management strategies being considered here. Given what we have seen elsewhere in the basin, how might the stream be managed through this reach to preserve/restore water quality?
OHM 2019: Error in UTM, it should be 557436E not 567436E.

STOP BK1. Exposed Willow Moraine.
This cutbank exposes a complex sequence of interbedded till and lacustrine sediments currently being studied by Andrew Kozlowski and colleagues from the New York State Museum as part of surficial geologic mapping of the quadrangles in this area. A lower, consolidated till is overlain by some 18 till units interbedded with lacustrine sediments. This exposure illustrates the complexity of glacial deposits in the Upper Esopus watershed and highlights the difficulties in mapping stratigraphy — and identifying possible sources of suspended sediment turbidity into Esopus Creek and its tributaries.

STOP BK2. Landslide in Glacial Deposits.
A landslide along the right bank of Beaver Kill has propagated as much as 70 m upslope and at least 70 m along the channel downstream of the Hwy. 212 bridge (Figure 22). This site is a dramatic representation of several similar stream bank erosion/hillslope mass failures in the confined portions of the Beaver Kill watershed that seem to be significant sources of bed load sediment supply resulting in numerous gravel/cobble bars that induce further lateral erosion of the channel. An assessment of this stream corridor is planned for late summer 2009.

STOP 8. Meander Bend Migration on Esopus Creek at Beechford.
The meander of Esopus Creek just upstream of this location has been migrating eastward and downstream, as recognized from comparison of aerial photographs from 1959, 1980, and 2001 (Miller, 2009; Figure 23). The channel here appears to have been left (east) of the island on the 1903 topographic map. By 1959, the channel had avulsed to the right (west) side of the floodplain, though the original channel was still occupied (at least in part) as a secondary channel, creating a mid-­channel island. We do not know exactly when this occurred, nor whether this was a natural avulsion or was induced to protect the Hwy. 28 alignment. However, the main channel has been migrating eastward since 1959, eroding the island and creating a point bar on the right (west) bank. This continuing meander migration likely will result in reoccupation of the original channel and could threaten the Hwy. 28 alignment in the future.