Do soils and sediment block drains?

How Soil and Sediment Lead to Blocked Drains

When soil and sediment enter drainage systems, they accumulate and narrow the drain pipe, leading to restricted water flow and blockages.

Heavy rains and storms can cause soil erosion, leading to fine sediment being washed from the land into drains and pipes. Activities like construction and land clearing can also expose soil that may then enter drainage systems when it rains.

As sediment continues to build, it limits the volume of water that can pass through the pipe. Sediment buildup makes pipes vulnerable to tree root infiltration, which can fracture drain pipes.

Debris and other materials can subsequently get trapped, which can cause a full or partial blockage. Partial blockages slow drainage, while full blockages lead to backups and flooding.

Besides being inconvenient, blocked drains pose a hazard as they can cause water damage to walls and foundations. Stagnant water increases health risks by fostering mould growth and contamination in drain pipes. A study indicated that increased sediment loads in streams reduced insect diversity by 38% through disruption of their food sources.

Mitigating soil erosion is essential to maintain unobstructed water flow through drains, thus lowering sediment accumulation. Proper land management, erosion control barriers, and adherence to construction best practices help prevent sediment from entering drainage systems.

Common Sources of Soil and Sediment Buildup

There are several common sources that contribute soil and sediment buildup in drains in Plumpton and the greater Sydney area:

• Construction sites - Clearing land, digging, and moving heavy equipment over bare soil causes erosion. Heavy rainfall washes this loose sediment from sites into stormwater drains.
• Land clearing - Removing vegetation exposes soil to wind and rainfall erosion. Sediment enters local creeks and drainage infrastructure.
• Road and driveway runoff - Erosion occurs alongside impervious surfaces, allowing soil sediment to flow into drains with stormwater.
• Riverbank erosion - Sections of the Hawkesbury River passing through the area see crumbling riverbanks adding sediment load to the waterway and connected stormwater pipes.
• Agricultural areas - Cleared grazing land and crops in the greater Sydney region experience topsoil loss, contributing sediment buildup in drainage systems.

With Plumpton situated beside Prospect Creek that leads to the Hawkesbury River, sediment pollution entering local waterways can have significant downstream impacts. Proper land management and erosion barriers deployment on cleared land are crucial in averting drainage complications.

Consequences of Sediment Pollution

Beyond blocking drains, soil sediment pollution has concerning impacts on water quality, aquatic ecosystems, and overall environmental health.

High sediment loads flowing into waterways reduce clarity, blocking sunlight from reaching aquatic plants. Research indicates that sediment pollution can decrease water transparency by up to 90% in certain rivers. Diminished plant growth affects the entire food chain, as sediment depletes waterways of oxygen.

Diminished light penetration from sediment additionally hinders the photosynthesis of marine algae and seagrasses, crucial nursery grounds for fish. Research in Australia discovered that persistent sediment pollution led to 81% less seagrass density over a 50 year period.

Aquatic species also endure immediate physical harm from sediment. Fine particulate can clog gills and suffocate fish. High turbidity from sediment increases fish egg and larvae mortality rates.

Sediment smothers river gravel beds used by fish to lay eggs and shelters invertebrates.

Nutrients, such as nitrogen and phosphorus, bind with sediment particles, fuelling the growth of harmful algal blooms. Such algal blooms severely degrade water quality and can be toxic to aquatic organisms. Pollutants including metals, oils and toxic chemicals also bind to sediment, entering food chains from small invertebrates up to fish and birds.

With higher runoff rates carrying soil sediment into drainage systems, the consequences span from blocked pipes locally through to impaired regional water health and biodiversity threats. Preventing erosion and sediment escape from the land is key for ecological sustainability.

Preventing Sediment Buildup

There are several effective methods households and businesses can employ to prevent soil and sediment from entering drainage systems.

Stabilise Exposed Soil

Bare soil is highly vulnerable to erosion, so stabilising areas of exposed earth is critical. Techniques include:

• Plant native grasses, shrubs or trees to establish roots that bind soil. Aim for at least 70% ground coverage.
• Install erosion control barriers like silt fencing, organic mulch berms or rock check dams on sloped land to capture sediment.
• Apply natural fibre blankets or hydroseeding mixtures to disturbed areas accelerate vegetation regrowth.

Manage Stormwater Onsite

Capturing and treating stormwater before it enters drains also prevents sediment pollution. Options such as:

• Rainwater tanks to collect and repurpose roof runoff.
• Rain gardens, swales, and infiltration trenches facilitate water infiltration into the soil, filtering sediment in the process.
• Settling ponds or retention basins allow sediment to settle before the water is discharged.

Improve Land Drainage

Soil that’s well-aerated and rich in nutrients, with stabilised plant roots, resists erosion effectively. Subsurface land drainage systems encourage rainwater to penetrate the soil rather than contribute to surface runoff. This encourages vegetation growth, nutrient uptake and erosion control.

With informed planning, managing soil stabilisation, stormwater treatment, and drainage can minimise sediment pollution from urban and rural lands. By stopping sediment from reaching local waterways, we also prevent it from clogging drain pipes.

Using Silt Bags for Drain Protection

Silt bags are an efficient, eco-friendly way to shield drains from excessive sediment. Installed around storm drain inlets, these mesh fabric sacks capture runoff sediment, filtering it from the water before entering drainage infrastructure.

For continued effectiveness, silt bags require regular monitoring and need to be emptied once they become full.

Benefits of Using Silt Bags

• Prevent sediment and debris blocking storm drains or pipes downstream
• Improve water quality by filtering pollutants from runoff before entering waterways
• Support natural water filtration processes instead of using chemicals or energy-intensive methods
• Easy to install around existing drains and removable once site stabilises
• Made of biodegradable natural materials like coir or jute fibre

Positioning silt bags around storm drains receiving runoff from construction sites, exposed soil areas or alongside impervious surfaces provides an accessible sediment control option. As a component of wider drainage and erosion management, silt bags offer a sustainable solution for enhancing water quality through passive treatment.

Compared to techniques like sediment traps or active pumping systems, they utilise a purely physical process for sediment removal without chemical inputs. Placing silt bags at drainage collection points can protect against sediment accumulation damage to drain pipes and infrastructure.

Land Drainage and Environmental Impact

Installing land drainage systems can benefit the environment when well-designed, but conventional drainage methods often overlook sustainability. Focusing on water quality and comprehensive soil management during drainage projects helps minimise nutrient depletion and sediment issues.

Sustainable Drainage Design

Carefully assessing on-site conditions and drainage interactions supports ecological solutions. Techniques like subsurface pipes, biodrainage channels, detention ponds, and vegetated swales promote the absorption and plant filtration of rainwater, ensuring a controlled downstream release. These methods not only reduce rapid surface runoff by boosting natural infiltration, but they also beautify landscapes.

Native, drought-resistant plants along drainage routes offer habitat and contribute to soil stability. Diverse vegetation filters and absorbs nutrients otherwise lost through leaching or erosion. Additionally, well-aerated soil boosts microbial activity, enabling efficient nutrient cycling.

Maintenance Protects Functionality

Routine inspections and maintenance preserve drainage function and allow for early detection of potential blockages. Techniques like drain jetting, descaling and suction removal target specific issues without disturbing surroundings. Telescopic cameras diagnose problems without digging, guiding precision repairs.

Silt traps, mesh guards and permeable filters at system inlets limit sediment entering pipes. Quickly addressing leaks or cracks prevents soil saturation and nutrient leaching.

Responsible Drain Cleaning

Inadequate drainage maintenance, particularly with toxic chemical cleaners, degrades water quality. These corrode infrastructure and endanger aquatic life being discharged. Enzymatic or microbial treatments offer an eco-friendly alternative to break down organics.

Addressing environmental impacts during the installation of land drainage can prevent problems such as erosion and pollution, thus promoting soil vitality and biodiversity.