Dowagiac River Restoration Final Assessment Report June 27, 2013 Prepared for: Pokagon Band of Potawatomi 58620 Sink Road Dowagiac, MI 49047 DOWAGIAC RIVER RESTORATION DOWAGIAC RIVER ASSESSMENT FINAL REPORT Prepared for Pokagon Band of Potawatomi 58620 Sink Road Dowagiac, MI 49047 Prepared by Inter-Fluve, Inc. 301 S. Livingston St., Suite 200 Madison, WI 53703 608-441-0342 June 27, 2013 June 11, 2013 [2] DOWAGIAC RIVER RESTORATION TABLE OF CONTENTS INTRODUCTION ................................................................................................................................4 PROJECT GOALS ...........................................................................................................................4 CRITICAL ELEMENTS IN THIS REPORT .................................................................................................6 WATERSHED OVERVIEW ....................................................................................................................7 GENERAL ...................................................................................................................................7 HISTORIC IMPACTS .......................................................................................................................9 GEOLOGIC HISTORY .................................................................................................................... 13 Bedrock Geology .......................................................................................................................................... 13 Glacial Geology ............................................................................................................................................ 14 SOILS AND WETLANDS................................................................................................................. 18 FLORA AND FAUNA ..................................................................................................................... 20 FIELD ASSESSMENT RESULTS ............................................................................................................. 22 GEOMORPHIC ANALYSIS .............................................................................................................. 22 upper watershed condition ......................................................................................................................... 22 Existing project reach Conditions ................................................................................................................ 31 Historic Conditions....................................................................................................................................... 36 SEDIMENTATION ........................................................................................................................ 43 Depth of Refusal Survey .............................................................................................................................. 43 RODGERS POND ........................................................................................................................ 49 HYDROLOGIC ANALYSIS ............................................................................................................... 53 Flood Magnitudes ........................................................................................................................................ 54 Base Flows ................................................................................................................................................... 57 Changes to watershed hydrology ................................................................................................................ 58 HYDRAULIC ANALYSIS ................................................................................................................. 62 Existing Conditions....................................................................................................................................... 63 Proposed Conditions.................................................................................................................................... 66 Project-Related Changes ............................................................................................................................. 67 DESIGN RECOMMENDATIONS ............................................................................................................ 76 PLAN FORM ALIGNMENT OF DOWAGIAC CHANNEL............................................................................. 76 DOWAGIAC CROSS SECTIONAL GEOMETRY ....................................................................................... 80 HABITAT ELEMENTS OF RESTORED DOWAGIAC CHANNEL ..................................................................... 81 Floodplain Habitat ....................................................................................................................................... 81 In-Channel Habitat ....................................................................................................................................... 82 RODGERS LAKE OUTLET ............................................................................................................... 88 CONSTRUCTABILITY AND COSTS ..................................................................................................... 89 CHALLENGES AND FURTHER INVESTIGATION FOR FINAL DESIGN ............................................................. 90 REFERENCES.................................................................................................................................. 91 APPENDIX A – MAPS ...................................................................................................................... 94 APPENDIX B – RESULTS OF TREE SURVEY ............................................................................................. 94 APPENDIX C – PHOTO LOG ............................................................................................................... 94 June 11, 2013 [3] DOWAGIAC RIVER RESTORATION INTRODUCTION The Pokagon Band of Potawatomi Indians are one of the only native american tribes within the midwest that reside on their ancestral lands. Though many of the Potawatomi people were subjected to the forced removal policy of the US government and moved to reservations in the west, a small band under the direction of Chief Leopold Pokagon were able to remain. Silver Creek and Pokagon Townships within Cass County encompass most of the current land holdings of the tribe. The Dowagiac River flows through these townships and within tribal lands. True to the tribal culture of respect for Mother Earth, the band has endeavored to heal historic impacts created by the channelization of the Dowagiac. The management of waterways has evolved across the nation as science has illuminated the correlation between healthy river corridors and clean drinking water, flood abatement, and nutrient processing among a multitude of other beneficial relationships. No longer are the goals of development (primarily agriculture here) and healthy rivers in opposition, with techniques to successfully accomplish both well understood and proven. Benefits of healthy river systems for fishing, hunting, paddling, and the general aesthetics of a natural system are valued in both urban and rural communities. For these reasons many local stakeholders are seeking river revitalization as both an economic and ecological positive for the community. Figure 1. The valley of the historic Dowagiac River is very similar to this drawing. Channelization in the early 1900s cut a straight channel through the valley, restoration seeks to return to this more natural condition, depicted here. PROJECT GOALS The boundaries for this restoration project run approximately from Peavine Street to just above Crystal Springs Street at the tribal property boundary. Discussions with tribal biologists have outlined a set of Project Goals that are used to inform and guide the design approach. Goals were developed specific to the two major elements of the river corridor, the river channel itself, and the floodplain on either side of the channel (Figure June 11, 2013 [4] DOWAGIAC RIVER RESTORATION 2). Project goals have been discussed with the tribe and categorized into goals related to the channel proper and the adjacent floodplain of the system. Dowagic River Channel Increase frequency of pool habitat and riffle Increase the frequency of large wood habitat, habitat (if appropriate) both single logs and jams Restore sinuosity and meanders to near pre- Maintain recreational passage through the channelization conditions channel Re-establish more natural patterns of scour Eliminate or minimize flood profile changes and deposition to create bed heterogeneity upstream that may impact adjacent neighbors Dowagic River Floodplain Increase the frequency and extent of Preserve and increase microtopographic floodwater accessing the floodplain features that develop complex habitat types on the floodplain Breach or remove levee spoils placed during Re-establish or maintain tribally significant channelization in the early 1900s vegetation within the floodplain Ecological goals will be accomplished through a return to the pre-disturbance channel. This report centers on the understanding of historic phases of manipulation to the watershed and the river corridor itself that resulted in todays Dowagiac River system. By understanding