Rivermouth classification as a tool for guiding restoration

Transcription

1 Rivermouth classification as a tool for guiding restoration JEFF SCHAEFFER 1, J. C. NELSON 2, AND JAMES H LARSON 2, 1 USGS Great Lakes Science Center 2 USGS Upper Midwest Environmental Sciences Center U.S. Department of the Interior U.S. Geological Survey

2 The importance of rivermouths Where humans interact with the Great Lakes Commercial shipping and recreational boating Fishery and Wildlife Resources Fish nurseries waterfowl

3 What are they like now? Tremendous interest in restoring rivermouthsbut how? Provide managers with tools that give predictable outcomes We began to study them intensively in 2011

4 Defining rivermouths Mixing Rivermouth zone Can extend from far upstream to well offshore A mixing zone

5 Classification data base NHD Mined spatial databases Found three distinct types of data River Characteristics Stream order Watershed characteristics Land cover Rivermouth (most calculated) Area, estuary type

6 Rivermouths are abundant Each red dot represents a rivermouth About 2100 rivermouths on the U.S. Shoreline Evenly distributed among lakes 1 per 4 km of shoreline

7 Most rivermouths arise from small rivers 800 Coastal Rivers Farm Ranch Interior Rivers Number of Rivers Township Small National Parks Yellowstone NP 0 <100 <1000 <10K <100K <1000K <10000K Watershed area (Ha) Only 7 large rivers in the Great Lakes Saginaw, Grand, Maumee

8 Rivermouth Areas Among Lakes Ha / km of U.S. Shoreline Actual SUP MICH HUR ERIE ONT Lake Ha / km with Lake Huron scaled to Huron scaled to 1 SUP MICH HUR ERIE ONT Lake Based on estimated areas only, But MICH, ERIE, ONT times RMZ area/shoreline as do others

9 Rivermouth Channel Types 2500 Number Total is % of all rivermouths are single channel How many used to have deltas? Braided and Delta found only in upper lakes! 0 Single Braided Delta Channel Type

10 Estuary types Direct Number DIR upper lakes BAY even DROWN even BAR Sup, Erie, Ont No fjords or tectonic estuaries! Embayment Drowned rivermouth DIR BAY DROWN BAR Estuary type Bar-Built

11 River (scale varies with watershed size) Flow Rivermouth (local scale) Lake (scale varies from local to regional) Backflushing Watershed size ( S,M,L) Channel Length (km) Thermal regime (C, CT, WT, W) Flow (L,M,H) Slope Watershed attributes % forest, % agricultural % urban, % wetland Flow attributes (Seelbach et al. 1997) Water chemistry (Seelbach et al. 1997) Network vs. single drainage Estuary type Drowned river mouth Direct to Lake Embayment bar-built lagoon Fjord (not in GL) Tectonic (not in GL) Valley type (From Seelbach et al. 1997) Wetted perimeter or Channel Single Braided Delta or Length of mixing zone or surface area of estuary Dredging (Yes, No) Lake Lake Region Local Wetted perimeter or Channel Single Braided Delta Distance to 37 m depth Fetch Pick no more than 5 attributes, With categorical assignments based on distributions. The 1 st classification will be hierarchical 1 st Classification Watershed size rivermouth area 2 nd Classification Predictions about mixing, fish communities

12 Simple and familiar characterization Stream order 1 st, 2 nd 3 rd or higher Coastal Drainage Interior drainage The Rivulets Medium Large Open Closed

13 Coastal drainages, aka the rivulets Small watersheds (<100 ha), direct discharge most intact watersheds are in Superior Mixing in the lake proper About 1800 of our 2092 RM s (86%) Fish passage issues are surprisingly common Thermal characteristics and flows vary Watershed, fish passage, woody debris

14 Medium Rivers Stream order 1 st, 2 nd 3 rd or higher Coastal Drainage Interior drainage The Rivulets Medium Large Open Closed

15 Restoration: medium rivers You get vegetated watersheds or intact rivermouths, but rarely both Peshtigo: natural delta and braided channel, agriculture in watershed Ausable: intact watershed, but heavily modified rivermouth Ford: both, orders of magnitude more larval fish than other streams

16 Restoration: medium rivers Open Enclosed Deltas, Braids Many now channelized Wetted perimeter, lengthens river habitat Embayments, Bar-built lagoons, Drowned RM s Protected mixing zone, Retain sediment, wetlands Restoration requires rivermouth habitat, fish access, and a reasonably intact watershed

17 Ausable River Oxbows Former channel

18 Large Rivers Stream order 1 st, 2 nd 3 rd or higher Coastal Drainage Interior drainage The Rivulets Medium Large Saginaw, Grand, Maumee, St. Joseph, Fox, Oswego, Menominee, Maumee

19 Greatest challenge will be large rivers They are rare Their watersheds are modified heavily Nearly all have been developed as shipping ports But big river habitats are needed for many fish species

20 The solution may be found in AOC s Areas of Concern Originally listed as sites where contaminants were an issue They are potentially great places: future habitats, new jobs, good planning, stakeholder involvement They are an opportunity that we might take AOC s are likely to be the sites where restoration will be undertaken. These are the sites where local economies will be rejuvenated via improved environmental quality.

21 Acknowledgments Funding provided by: Many thanks to: Jeff Allen, Margi Chrisinske, Glen Black, Mike Wiley, Jon Valazza, David Bennion, Rich Quintal, Gen Ito, Jim Nicholas, Paul Reneau, Don James, Tom Weaver, Denis Scanlan, Eric Dantoin, Dan Wydra, Neal Craig, Peter Hughes, Natalie Amoroso, Jennifer Granneman, Larissa Herrera, Tim O Brien