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Arkansas

Arkansas' Dynamic Delta Rivers

Summer 2008

Delta rivers in the Natural State face serious threats and are generally in poor health. As the spring floodwaters in east Arkansas receded, revealing further erosion on rivers throughout the region, Cache River Project Manager Josh Duzan and Delta Project Manager Matt Lindsey discussed conservation issues that drive their work.

Q:

What is the big-picture objective of the Conservancy's work on rivers in east Arkansas?

A:

Matt: Understanding the needs of healthy rivers and the needs of people in the region, and then addressing challenges and ensuring the critical needs of people, animals, plants and the environment are met in a sustainable way.

Q:

What big rivers do you focus on, and what are some of their major problems?

A:

Josh: We focus on the White, Cache and Black rivers as well as Bayou DeView and Bayou Bartholomew. Their biggest problem is excess sediment due to the instability of these river systems as a whole. You don’t see an eroding bank here or there. You see massive erosion – the tell-tale sign of river instability – over the entire reach of the system.

Q:

What caused the instability?

A:

Josh: In 1927 there was the largest flood in recent history in the Mississippi River basin. Around 26,000 square miles were inundated, including most of eastern Arkansas. After the flood, Congress passed the Flood Control Act of 1928, which authorized a large-scale flood control project on the Mississippi River and some of its major tributaries. The project included the construction of levees, floodways, channel cut-offs, revetments, dikes and dredging on the Mississippi River. These actions basically straightened the Mississippi River, sped it up and deepened its channel. Over time, the channels of the lower Mississippi’s major tributaries have deepened to match the lowered bed of the Mississippi River.
Matt
: Projects mandated by the Flood Control Act have done a good job of protecting the land and people from catastrophic floods, and that’s important. But the negative effects on our rivers and the environment weren’t anticipated.

Q:

Why are deeper, straighter channels in the Delta a problem?

A:

Matt: Meanders and floodplains are energy release valves for rivers. In a natural system, a river has twists and turns to slow it down. When it gets too full, it spills over into the floodplain and slows down. When river channels are straightened and deepened, they have less access to these release valves. The energy has to go somewhere, so it goes downward and cuts the channels even deeper. It’s a compounding problem.
Josh: Some of the first explorers to this area noticed localized erosion at several spots on the Mississippi River and other bottomland rivers. What we see today, though, is extensive erosion along hundreds of miles.

Q:

How does that affect the ecosystem?

A:

Josh: Species that live in the rivers and surrounding forests are adapted to natural flooding and sediment cycles. Flooding brings nutrients to the plants and animals, and seasonally flooded areas are essential nurseries for many species. When deepened channels reduce flooding, species like red maple start to grow where bald cypress and tupelo are drying up. In addition to a shift in forest types, we’ve seen a vast reduction in native fishes and mussels and an increase in species that are more tolerant of pollution and increased sediment levels.

Q:

You mentioned the Flood Control Act of 1928; is anything happening today or planned for the future that would exacerbate these problems?

A:

Josh: Maintaining the flood control projects and navigation channels is an on-going effort that degrades the health of Delta rivers. On the White River, the U.S. Army Corps of Engineers is mandated under the Flood Control Act to maintain an 8-foot-deep channel from the Mississippi River upstream to Augusta and a 4.5-foot-deep channel from Augusta upstream to Newport. This involves dredging to allow barge traffic up and down the river.
Matt: There are also proposals to deepen the current navigation channel on the White River, and to extend its navigation channel from Newport to Batesville.

Q:

What effects might deepening the White and extending its navigation channel have on the river?

A:

Josh: That stretch, from Newport to Batesville, is unique because it hasn’t been dredged. Dredging it would destroy habitat like gravel shoals that are critical to mussels and spawning paddlefish.
Matt: Additional dredging would increase sediment, which affects sport fish like largemouth bass and crappie. They are sight-feeding fish, and sediment reduces their efficiency. These fish also need a cyclical connection to the floodplain and outlying oxbow lakes to maintain healthy reproduction. Deepening the channel means the river would have even less access to its floodplain.

Q:

What effects might deepening the White have on its tributaries?

A:

Josh: Rivers are connected. Altering the lower White River will have dramatic effects on all its tributaries, including the Cache River. As these tributaries react to changes on the White, their tributaries – in turn – will have to adjust. They’ll dig themselves deeper and further increase sediment downstream. It’s a giant ripple effect.
Matt: The soils of the Mississippi River Valley are especially vulnerable to this sort of degradation. There’s no bedrock to stop the erosion. A headcut – a place where the water digs into the riverbed – could run hundreds of miles upstream.

Q:

What is the Conservancy doing to address the problems facing Delta rivers?

A:

Matt: We’re working with farmers, the Corps of Engineers and others to restore certain areas and manage the rivers sustainably. We’ll never be able to return these rivers to their natural state, but we can manage them in a way that will help stabilize them and protect the valuable services they provide to both people and nature.
Josh: The Conservancy works with partners to provide the science to help guide management practices or policies. In 2003, with funding from the Natural Resource Commission, we completed a study of the Cache River to develop a baseline assessment of its sediment flows and bank erosion rates. It helped us identify sources of sediment. Now, as we begin restoration projects, we’ll be able to measure against the baseline to see if conditions are improving. We’re currently surveying the Black River as well.
Matt: We continue to look for opportunities to conserve more land surrounding key rivers through conservation easements or acquisition. Conserving riverside land goes a long way toward improving the overall health of river systems.


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