Poorly constructed roads have potential to create flashier streams and increase sediment delivery to streams from chronic erosion and episodic erosion events:

Roads Create Flashier Streams 

• Poorly constructed roads collect and concentrate surface stormwater flows from the landscape 

• Concentrated flow from the road network enters the stream system with greater volume and velocity than what the stream would normall experience. The increased energy of the water causes the stream channel to incise, which may ultimately lead to bank erosion and lowering of the water table

• Since roads collect and channel water moving across the surface, less water ends up recharging the groundwater basin, which decreases summertime stream flows and leads to drier soils downhill of the road

When roads collect, concentrate, and deliver runoff to streams they create flashier stream flows

Roads Increase Chronic Erosion and Sediment Delivery

• Roadways and road-side ditches accumulate fine sediments during the dry season

• During most storms, as water flows across the road surfaces and ditches, it picks up the accumulated fine sediments and can eventually deliver them directly to the stream system

• Erosion and sediment delivery occurs during every storm that produces runoff; it's a chronic process

• Unpaved roads contribute more sediment to streams via chronic erosion than paved roads because they have much more erodible surface area 

Chronic sediment delivery occurs when road surface drainage is constantly eroding the road or ditch surface and is connected to a stream

Roads Increase Episodic Erosion and Sediment Delivery

• Large storm events, earthquakes, and other factors can create large scale erosion events that end up resulting in large pulses of sediment being delivered to streams

• This type of erosion is episodic, it occurs in pulses and not at a constant or predictable rate

• Example: Steep cutbanks associated with roads may fail in response to storm events or other triggers, such as earthquakes

• Example: Stream crossings may flood and washout during floods

• Example: Flooded roads may produce gullies in the fill slope

When culverts flood, due to plugging or improper sizing, large amounts of sediment near the stream crossing is vulnerable to erosion and delivery to streams

Visit this page to get more information about designing and maintaining roads in order to minimize erosion. 

UPGRADE ROADS

Storm-proof roads so that they are resilient to 100-year peak storm flows without negativley impacting streams. 

• Remove unstable sidecast and fill material from steep slopes
• Apply road drainage techniques such as rolling dips and outsloping to improve dispersion of surface runoff and reduce road length that directly drains to stream channel
• Add rock as needed to fortify roads and crossings
• Add single-post trash racks at culvert inlets to reduce potential for culvert plugging
• Ensure stream crossings have fail-safe features to direct flood waters back into natural stream channel

Before - culvert is undersized and placed at shallower angle than stream channel; culvert is fish passage barrier

 

After - bridge spans channel so that there is minimal disturbance of road crossing to creek flow and habitat

 

Before

After

DECOMMISSION ROADS

If road systems are no longer needed to manage a property, they can be decommissioned such that their impacts, are erased from the watershed. Landowners can elect for complete decommissioning, or long-term winterization of the roads, which gives them the option to re-establish roads in the future. 

• Drainage structures, like culverts, and fill material are completely removed
• Excavated material from crossing may be relocated to cutbanks to promote vegetation growth or hauled to stable locations
• Decompact all lengths of road that drain to stream crossings and construct cross-road drains and/or partial outsloping to reduce chronic erosion and promote vegetative growth

CONVERT ROADS TO TRAILS

A hybrid between road upgrading and decommissioning.    

• Reduces road width to 4-6 ft. along entire road length to allow access by hikers and quads
• Completely excavate some stream crossings, partially excavate others, depending on needs of hike and quad access 
• Excavate unstable sidecast or fillslope materials on downslope
• Stockpile excavated material at a stable site
• Apply storm-proofing road drainage techniques to all road length draining to stream crossing to improve dispersion and surface runoff 

Before

After

• Video - A video (26 mins.) about roads and how they influence the watershed.
• Handbook for Forest and Ranch Roads - Mendocino County RCD, Handbook for Forest and Ranch Roads. Available in English and Spanish.
• Private Road Maintenance Guide - Santa Cruz RCD, Central Coast Private Road Maintenance Guide (Good resource for landowners)

• Handbook for Forest and Ranch Roads - Mendocino County RCD, Handbook for Forest and Ranch Roads. Seen as BMPs by RWQCB, CDFW, CalFire, and USDA NRCS. Available in English and Spanish.
• California Salmonid Stream Habitat Restoration Manual - CDFW, California Salmonid Stream Habitat Restoration Manual, Part IX discusses the evaluation of stream crossings for fish passage and Part X discusses BMPs for rural roads maintenance and design. (Comprehensive technical resource for professionals) 
• Private Road Maintenance Guide - Santa Cruz RCD, Central Coast Private Road Maintenance Guide (Good resource for landowners)
• BMPs for public roads - Napa County Public Works, Guidelines for County Road Maintenance Practices that Protect Aquatic Habitat and Salmon Fisheries
• USDA Low-Volume Roads Engineering BMPs Field Guide - Guidance for road builders, road
  managers, and resource specialists in most geographic areas to help build better, more cost-effective
  roads, and roads that minimize adverse environmental impacts and protect water quality.

•  Storm-Proof Roads Checklist 
• Typical Drawings - Typical drawings for common storm proofing treatments. Click on "Managing Unpaved Roads" for full menu
• Landsmart® Program - Technical assistance for land managers related to roads and watershed concerns