The Good, the Bad, and the Ugly of River Management. Julie Moore, P.E. Stone Environmental February 7, 2012

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1 The Good, the Bad, and the Ugly of River Management Julie Moore, P.E. Stone Environmental February 7, 2012

2 Agenda Traditional approach to river management Common flood and flood recovery myths Role of river corridor protection Flood recovery guidelines 2

3 We like to live next to the water Photo credit: Vermont DEC

4 And we like our rivers straight and simple

6 Traditional Approach to River Management = CONFINEMENT Confined rivers result in: Increased flooding Altered sediment regimes Increased channel instability Reduced habitat quality Excessive nutrient export

7 Common Flood Myths You can dig yourself out of a flood. Rivers move water, sediment, and woody debris. The shape of a natural river channel reflects a balance between the flow and the amount of sediment and woody debris that the stream carries. The wider and deeper a channel is, the slower the water moves, making it more likely that excessively large sediment bars will form. In channels in a narrow valley, digging deeper usually leads to more down-cutting and collapse of the banks. 7

8 Common Flood Myths It is possible to ensure against flood damage by straightening and armoring stream channels. There is no way of completely avoiding future flood damages other than removing all permanent infrastructure from predicted flood inundation and erosion hazard areas Armoring banks and straightening channels provide short-term fixes that will be effective until the next large flood Can have the unintended consequence of increasing downstream flooding and erosion risks 8

9 We need to move away from the concept that rivers are static systems Photo credit: Vermont DEC

10 Common Flood Myths Cutting trees down in the floodplain will prevent debris jams during the next flood. Large numbers of trees can be carried down river during extreme events clogging bridges and culverts, depositing on islands, and making local flooding worse in some areas Post-flood surveys in Vermont indicate that: Wide forested floodplains stayed intact and the trees captured and retained flood debris Tree loss was most abundant along narrow buffers and thin stands in floodplains Design and planning is needed to consider the expected load of trees and other debris that may be moved down river during future floods. Photo credit: Roy Schiff, Milone & MacBroom 10

11 Common Flood Myths This was the 100-year flood so we will never see another flood like this during our lifetime. The 100-year flood has a 1% chance of occurring in any given year The northeast is seeing larger and more frequent flooding Over the past several years more large storms have taken place than the gage statistics suggest should be happening. 11

12 Common Flood Recovery Myths It is okay to fill in widened channels and floodplains. Many channels expanded two to ten times pre-flood widths, effectively forming floodplains during the flood The post-flood channel shows the space the river needs to convey the water, sediment, and debris during a large flood Filling should be as limited as possible to minimize future flood and erosion risks Photo credit: Lars Gange & Mansfield Heliflight 12

13 Common Flood Recovery Myths All of the aquatic life is dead after such a large flood so it does not matter what we do to our rivers now. Fish and insects that live in streams have amazing survival instincts because of their dynamic home Although mortality does happen during stressful times such as floods or droughts, these disturbances are actually an essential part of the aquatic ecosystem Floods regenerate the bed by moving large amounts of sediment, clean the channel of waste and decayed material, and create new habitat features 13 Photo credit: Louis Porter, CLF

14 Common Flood Recovery Myths All sediment should be scraped off of floodplains. Size and quality of newly deposited river sediment can widely vary Whenever possible, deposited sediment should be left in-place or incorporated into active fields Selective removal of the coarser or contaminated parts of the deposited sediment should be considered Photo credit: Lars Gange & Mansfield Heliflight 14

15 Common Flood Recovery Myths The replacement of failed culverts and bridges with structures of the same size is suitable. Culverts and bridges fail due to high flows, plugging with sediment and trees, and water flowing around the structure Many failed structures were improperly designed or installed Paying once for a larger structure that fits the stream channel is more economical than replacing smaller structures that repeatedly fail Photo credit: Lars Gange & Mansfield Heliflight 15

16 Escalating Costs, Risks, and Ecosystem Degradation Floods and Property Damage Encroachment 16 Dredge, Berm and Armor

17 Breaking the Cycle Flood amnesia often sets in within a period of months following a flood event Slowly and steadily we revert to old practices, which leaves us little better prepared for the next event River corridor protection can be key to breaking the cycle of armor encroach damage & loss 17

18 Functioning floodplains and river corridors create an intersection for the protection of public values Public Safety and Property Protection Floodplain Protection & Stream Equilibrium Ecological Integrity and Fish & Wildlife Resource Water Quality and Quantity

19 Approaches to River Corridor Protection Technical and financial assistance to municipalities and individual landowners Most land use decisions are made at the local level Map and protect fluvial erosion hazard (FEH) zones Important to distinguish between erosion and inundation hazards Link Clean Water Act objectives with flood hazard avoidance/mitigation Municipalities and landowners are often more motivated to reduce exposure to flood impacts

20 Key Strategies: Zoning Avoid future conflicts Using FEMA-driven flood insurance mapping to educate municipal officials about the importance of river corridors Vermont has developed model river corridor protection ordinances Work with state and federal programs to create/identify incentives financial and programmatic for river corridor protection

21 Municipal zoning

22 Key Strategies: Easements Easements can be used to augment zoning Restrict channelization practices and unnecessary efforts to stop all erosion Passive restoration relies on river (and time) to reestablish meanders and floodplain Efforts need to be coordinated closely with other land conservation programs such as: Federal farm service agencies Local land trusts

23 River Corridor Easements Map credit: Vermont DEC

24 Key Strategies: Restoration Active - use of big yellow machines Needs to be strategic, as actively reconnecting rivers with historic floodplains is extremely expensive Allows for immediate gain in floodplain storage of sediment and debris Can help alleviate localized flooding Passive let nature run its course Unpredictable Things may get worse before they get better

25 Active Restoration AFTER BEFORE

26 BEFORE: Existing railroad embankment Photo credits: Roy Schiff, Milone & MacBroom AFTER: Railroad embankment removed to floodplain elevation

27 Approaches to River Corridor Protection Successful river corridor protection: Engages municipalities and landowners Recognizes existing encroachments Seeks opportunities and partnerships Takes the long view

28 Flood Recovery Guidelines Carefully Consider ALL Options Weigh the needs of the built and natural environments Evaluate a range of alternatives for both short and long term, including: public safety infrastructure protection floodplain agriculture water quality aquatic habitat cost-effectiveness longevity Seek a preferred alternative that will benefit multiple objectives, aiding both the river and people Photo credit: Lars Gange & Mansfield Heliflight

29 Flood Recovery Guidelines Community Planning Recognize that flowing water does not respect political boundaries Think about watershed neighbors and how to minimize downstream risks Consider past and future flooding and how best to reduce risks from inundation, channel movement, sediment deposition, and woody debris Photo credit: Lars Gange & Mansfield Heliflight

30 Flood Recovery Guidelines Stay Committed Successfully reducing flood and erosion hazards is a challenging and long-term process It is essential if we are to create safer communities amongst healthier rivers in a mountainous region with many town and village centers located in floodplains Photo credit: Lars Gange & Mansfield Heliflight

31 Acknowledgments Mike Kline, Vermont DEC Roy Schiff, Milone and MacBroom Elise Annes, Vermont Land Trust

32 Questions? Julie Moore, P.E. (802)

Rhode Island NRCS received approximately $2.4 million in ARRA funds to implement four floodplain easement projects.

American Recovery and Reinvestment Act (ARRA) Emergency Watershed Protection Program Floodplain Easements Rhode Island Natural Resources Conservation Service Rhode Island NRCS received approximately $2.4