Latest news with #sediment
Yahoo
12-07-2025
- Climate
- Yahoo
Army Corp of Engineers attempting Arkansas River operation for the first time since the 1990s
RUSSELLVILLE, Ark. —An operation on the Arkansas River is underway that the Little Rock district Army Corps of Engineers has not done since the 1990s. Last month, a vessel grounded on a buildup of sediment between Ozark and Dardanelle that has slowly become a problem over the decades. Edmund How, Chief of Hydrology & Hydraulics U.S. Army Corps of Engineers Little Rock District, said the heavy flow upstream created the recipe to conduct a hinge pool operation. 'It's really neat to kind of have the right conditions to solve a problem in a more efficient way,' Howe said. Loose barge hits Terry Lock and Dam on Arkansas River By letting more water in, the Dardanelle dam is lowering the water levels to its north by six inches. That doesn't sound like a lot, but Howe explained that between the start of the operation on July 10 and the next day, the flow of sand at the trouble spot had more than tripled. It is called self-scouring. 'Like a kid dumping a bunch of sand down a slide. I comes down and the slide kind of sticks out so they can hop off very easily. What we're doing is effectively just taking the end of the slide and tilting it down a little bit further so that material keeps washing downstream into the deeper, much deeper parts of the channel,' Howe explained. Before the lock and dam system was built on the Arkansas River, parts of the river would dry up and become unnavigable during parts of the year. The hinge pool operation ensures that the traffic can go in both directions and the water level stays the same. Chief Public Affairs Officer of the U.S. Army Corps of Engineers Little Rock District Jay Townsend said they have to maintain a 9-foot depth channel for barges to travel. 'One 15-barge tow takes 870 18-wheelers off our interstate systems,' Townsend said. Lockmaster at Terry Lock and Dam recognized after man rescued on Arkansas River The alternative solution would be dredging, but that is more costly to taxpayers and disruptive to commerce. This operation is set to finish July 17, but rainfall and other factors upstream could change that. Copyright 2025 Nexstar Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
The Guardian
30-06-2025
- Science
- The Guardian
I'm obsessed with brittle stars: fish often nip off bits of their arms but they regenerate
Brittle stars have a lot of remarkable features as a species. Many of them are bioluminescent and can flash blue light; some will have patterns and do displays. These slender relatives of starfish can be very beautiful to look at and come in a range of colours – in the tropics, for example, they can be red, black or orange. And they've got spines all over them, so they can look quite ornate. They can also regenerate. Fish and other creatures will often nip off bits of their arms – known as sublethal predation – so they are constantly regenerating themselves. You can even break off all their arms, and sometimes even half the disc, and the brittle star will still regenerate. Brittle stars have the same radial symmetry and five arms as starfish but their arms are much thinner and can be 60cm long, depending on the species. People talk about the blue planet but I think of Earth as the brown planet, because most of the Earth's environment is the sea floor. It measures 361m sq km (140m sq miles) and is full of sediment – and where there is sediment, there are often brittle stars. In total, there are about 2,000 species of brittle stars and about half of these live at depths of more than 200 metres. As part of the Convex Seascape Survey, I have studied brittle stars all over the world. A lot rest on rocks or on the sediment surface, but my favourite species is the Amphiura filiformis, a burrowing brittle star found around British shores. Its centre disc is typically only 5mm wide and it's extremely numerous – in a 1 sq metre area, you can find up to 3,000 individuals of that species alone. It is my favourite species because it constantly turns over the environment and changes it, and you can see that happening in front of you; you can see the brittle star moving particles around and making mounds on the surface, injecting oxygen into the sediment, and breaking down the detritus that has fallen to the sea floor. When brittle stars such as Amphiura come up to the surface of the seabed, they put their arms up to catch particles passing by with the current. When currents become too slow or too fast, they will retract back down into their burrows and feed on the deposits by moving the particles down their arm to their mouth. I was the first scientist to obtain time-lapse footage of a population of burrowing brittle stars doing this. Nobody had seen their activities below, and I was struck by how active they were and how organised the population was, each at the same depth and neatly spaced apart like a row of soldiers. Brittle stars are essentially scavengers – they will eat particles of anything that is organic, including faecal pellets, the remains of dead fish that have fallen to the bottom of the ocean, and algae. They are extremely efficient in that way – they take in everything that is given to them. But since pollution settles at the bottom of the ocean and gets locked into the sediment, they are also very vulnerable. They are not like fish that can swim away; they are stuck in the sediment, they have to absorb it. When it comes to the climate crisis, brittle stars are the canary in the coalmine because their skeleton is made up of calcium carbonate: limestone, essentially. As temperatures warm and ocean acidification starts to spread, they are literally dissolving. They are also a keystone species. Like elephants in the savanna that knock trees down, which allows the grass to grow, they are constantly modifying their environment and making it more benign for other species. Because they do this so well and so efficiently, their presence alone enhances sea-floor biodiversity. Over the last half a billion years, we have gone through a huge diversification of life and brittle stars played a significant role in that. And they continue to have a significant role to play. So my hope is that one day we will recognise how vital these charismatic organisms are and put measures in place to protect them. As told to Donna Ferguson Martin Solan is a professor of marine biology at the University of Southampton
RNZ News
27-06-2025
- Business
- RNZ News
Bad rainstorm away from disaster: Why proposed forestry rule changes won't solve 'slash' problem
By Mark Bloomberg and Steve Urlich of During the past 15 years, there have been 15 convictions of forestry companies for slash and sediment discharges into rivers, on land and along the coastline. Photo: RNZ / Kate Newton Analysis - The biggest environmental problems for commercial plantation forestry in New Zealand's steep hill country are discharges of slash (woody debris left behind after logging) and sediment from clear-fell harvests. During the past 15 years, there have been 15 convictions of forestry companies for slash and sediment discharges into rivers, on land and along the coastline. Such discharges are meant to be controlled by the National Environmental Standards for Commercial Forestry, which set environmental rules for forestry activities such as logging roads and clear-fell harvesting. The standards are part of the Resource Management Act (RMA), which the government is reforming. The government revised the standards' slash-management rules in 2023 after Cyclone Gabrielle. But it is now consulting on a proposal to further amend the standards because of cost, uncertainty and compliance issues. We believe the proposed changes fail to address the core reasons for slash and sediment discharges. We recently analysed five convictions of forestry companies under the RMA for illegal discharges. Based on this analysis, which has been accepted for publication in the New Zealand Journal of Forestry, we argue that the standards should set limits to the size and location of clear-felling areas on erosion-susceptible land. In the aftermath of destructive storms in the Gisborne district during June 2018, five forestry companies were convicted for breaches of the RMA for discharges of slash and sediment from their clear-fell harvesting operations. These discharges resulted from landslides and collapsed earthworks (including roads). There has been a lot of criticism of forestry's performance during these storms and subsequent events such as Cyclone Gabrielle. However, little attention has been given to why the courts decided to convict the forestry companies for breaches of the RMA. The courts' decisions clearly explain why the sediment and slash discharges happened, why the forestry companies were at fault, and what can be done to prevent these discharges in future on erosion-prone land. New Zealand's plantation forest land is ranked for its susceptibility to erosion using a four-colour scale, from green (low) to red (very high). Because of the high erosion susceptibility, additional RMA permissions (consents) for earthworks and harvesting are required on red-ranked areas. New Zealand-wide, only 7 percent of plantation forests are on red land. A further 17 percent are on orange (high susceptibility) land. But in the Gisborne district, 55 percent of commercial forests are on red land. This is why trying to manage erosion is such a problem in Gisborne's forests. In all five cases, the convicted companies had consents from the Gisborne District Council to build logging roads. Photo: RNZ / Rebekah Parsons-King In all five cases, the convicted companies had consents from the Gisborne District Council to build logging roads and clear-fell large areas covering hundreds or even thousands of hectares. A significant part of the sediment and slash discharges originated from landslides that were primed to occur after the large-scale clear-fell harvests. But since the harvests were lawful, these landslides were not relevant to the decision to convict. Instead, all convictions were for compliance failures where logging roads and log storage areas collapsed or slash was not properly disposed of, even though these only partly contributed to the collective sediment and slash discharges downstream. Clear-fell harvesting on land highly susceptible to erosion required absolute compliance with resource consent conditions. Failures to correctly build roads or manage slash contributed to slash and sediment discharges downstream. Even with absolute compliance, clear-felling on such land was still risky. This was because a significant portion of the discharges were due to the lawful activity of cutting down trees and removing them, leaving the land vulnerable to landslides and other erosion. The second conclusion is critical. It means that even if forestry companies are fully compliant with the standards and consents, slash and sediment discharges can still happen after clear-felling. And if this happens, councils can require companies to clean up these discharges and prevent them from happening again. This is not a hypothetical scenario. Recently, the Gisborne District Council successfully applied to the Environment Court for enforcement orders requiring clean-up of slash deposits and remediation of harvesting sites. If the forestry companies fail to comply, they can be held in contempt of court. This illustrates a major problem with the standards that applies to erosion-susceptible forest land everywhere in New Zealand, not just in the Gisborne district. Regulations are not just "red tape". They provide certainty to businesses that as long as they are compliant, their activities should be free from legal prosecution and enforcement. The courts' decisions and council enforcement actions show that forestry companies can face considerable legal risk, even if compliant with regulatory requirements for earthworks and harvesting. Clear-felled forests on erosion-prone land are one bad rainstorm away from disaster. But with well planned, careful harvesting of small forest areas, this risk can be kept at a tolerable level. However, the standards and the proposed amendments do not require small clear-fell areas on erosion-prone land. If this shortcoming is not fixed, communities and ecosystems will continue to bear the brunt of the discharges from large-scale clear-fell harvests. To solve this problem, the standards must proactively limit the size and location of clear-felling areas on erosion-prone land. This will address the main cause of catastrophic slash and sediment discharges from forests, protecting communities and ecosystems. And it will enable forestry companies to plan their harvests with greater confidence that they will not be subject to legal action. This story was first published on The Conversation .
