Indiana University-Purdue University Indianapolis (IUPUI) / The frequency and magnitude of floods in the midcontinental United States have
increased in recent decades due to changing precipitation patterns as global temperatures
rise. These trends pose major social and economic risks to the region, which is home to
tens of millions of Americans and a global agricultural center. It is therefore critical to
understand if current fluvial dynamics are within the scope of past fluvial-climate
relationships, or if they represent a novel response to recent climate and land-use
changes. Presented is a 1600-year-long flood frequency record for the moderately sized
(~29,400 km2 watershed) White River, Indiana. Flood frequencies were determined using
14C-based sediment accumulation rates at Half Moon Pond, an oxbow lake on the lower
White River’s floodplain. Comparison with regional paleoclimate data shows that White
River flooding was frequent when atmospheric circulation resembled the negative mode
of the Pacific-North American (PNA) teleconnection, particularly during the Medieval
Climate Anomaly (950-1250 CE) and the Current Warm Period (last ~150 years). During
these times, the regional climate was dominated by warm-season precipitation originating
from the Gulf of Mexico. Conversely, White River flooding was less frequent during the
Little Ice Age (1250-1800 CE) when cold-season precipitation from the North
Pacific/Arctic dominated (+PNA-like conditions). The pre-1790 CE White River flood
history was antiphased with reconstructed Ohio River flood frequencies from southern
Illinois. This dynamic is consistent with discharge in small to moderate sized watersheds
being sensitive to rainstorm runoff and large watersheds being sensitive to snowmelt runoff. After 1790 CE, flooding frequencies of both river systems increased to their
highest levels, despite a shift to -PNA-like conditions. This change was likely due to
extensive Euro-American land-clearance, which increased runoff/erosion by reducing
evapotranspiration, interception, and infiltration. While the White River responded
strongly to climatic conditions in the past that were similar to present conditions (-PNA-like conditions), recent land-use practices have amplified the effects of the current
hydroclimate. Since a warming climate is expected to increase regional average
precipitation and extreme rainfall events, and that landscape modifications have lowered
surface resilience to hydroclimate events, flooding will likely become more frequent in
the coming decades.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/29142 |
| Date | 05 1900 |
| Creators | Wright, Maxwell N. |
| Contributors | Bird, Broxton, Licht, Kathy, Gilhooly, William, III. |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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