Approach
This approach targets actions focused on wetlands connected to, or adjacent to streams, rivers and other flowing surface waters. As hydrologic regimes change, driven by more extreme and variable precipitation, it is expected that the volume and rate of water entering wetlands will change. In Midwestern and Great Lakes watersheds affected by snowmelt, peak flood events are projected to shift to a month earlier, extreme low flows will shift from winter/spring to summer/fall, and soil moisture is expected to be lower during the growing season through the middle of the 21st century. This alteration in hydrology within waterways can degrade the structure and function of connected wetland ecosystems. Wetland types particularly vulnerable to degradation include those receiving water from currently unstable or altered hydrologic networks, including channelized streams and ditches. Stream channel alteration often results from land-use changes and related changes in runoff (observed in agricultural and urban areas), but also when flows are regulated, for example, after the physical re-routing and straightening of channel form by humans. Channelized flow creates deeper and straighter stream channels that become incised and potentially destabilized and wider, increasing flow velocity and reducing overbank flooding to riparian wetlands. Restoring and improving lateral connections of riverine systems can prepare wetlands to absorb excess water associated with extreme precipitation events, reduce peak flows, and reduce downstream flooding, as well as improve stream baseflow during droughts.
Tactics
- Re-meander channelized streams using natural channel design methods to slow the velocity of flow, create more habitat heterogeneity, and improve connectivity to adjacent floodplain wetlands.
- Re-sculpt functioning ditches to two-stage designs that mimic a floodplain to better handle large storm events by providing more consistent fluvial form and processes, as well as greater channel stability.
- Remove or modify levees, dams and other hardened infrastructure to restore a more natural hydrologic regime and to increase channel sinuosity and associated functions.
- Add culverts or alternative low-water crossings to roadways that impede flow and replace undersized culverts with larger culverts to improve natural stream-flow and debris-flow dynamics during flood events.
Strategy
Strategy Text
This strategy outlines resistance and resilience approaches to manage wetlands facing altered water budgets (water inputs, storage capacity, and outputs) due to a changing climate. Hydrology is a leading driver of wetland character and function and so expected changes to hydrologic regimes, hydrodynamics, and water levels concern wetland managers. Projections in the Upper Midwest indicate that wetlands will be influenced both by extreme precipitation and flooding events and longer drought periods between rain events. Some wetlands will become dryer and others may become wetter than long-term averages. Thus, managers face challenges (i.e., extreme flooding; drought) and opportunities (i.e., restored flood pulses to wetlands disconnected from surface or groundwater flows) in managing wetlands in the context of climate change. Restoring hydrologic connectivity has historically been a primary tactic of management efforts to restore wetlands lost or degraded by filling or draining due to land-use conversion and water extraction, and many of those same tactics can be applied or amended by wetland managers to meet climate change adaptation objectives. Restoring hydrologic connectivity and ameliorating saturated, anoxic conditions that limit decomposition also supports the capacity of wetlands to actively remove and sequester atmospheric carbon and mitigates future carbon losses.