salmon creek water conservation: stormwater management

8/3/2019 Salmon Creek Water Conservation: Stormwater Management

1/8

Salmon Creek

Water Conservation

ProgramConservation Strategy No.4:

Stormwater

Management for

Coastal California

Communities


2/8

OverviewIn many Caliornia coastal communities, reliable access to resh water is limited and watershed health andinstream ows are growing concerns. Current trends toward longer droughts and more severe stormsrender traditional methods o stormwater management ineective. Development o a robust, scalable,decentralized stormwater management strategy is critical or addressing watershed health and watersecurity.

Target community

All landowners, residents, businesses, and land managers in all coastal Caliornia communities whosestormwater runo is impacting natural waterways, especially those supporting endangered andthreatened species.

Potential eect

Implementation o eective stormwater management measures will result in the ollowing benefts,addressing both human needs and total watershed health.

Watershed:

Increasing uplands water infltration and retention capacity will improve water security by recharginggroundwater aquiers, while increasing base ows in streams and reducing mortality in endangeredfsh populations

Slowing down stormwater runo will decrease topsoil loss, erosion, ooding and stream ow varianceby reducing the volume and rate o peak ow events

Removing pollutants in runo will improve water quality in streams and aquiers

Reducing the delivery o erosion products to streams will increase ows by keeping pools and riesree o excessive sedimentation

Landowner:

Recharged groundwater supplies will increase water security by improving the unction o groundwa-ter wells and alleviate the economic and resource costs o trucking in water

Well-designed roads retain better drivability, with reduced maintenance needs

Reduced ooding protects property values and lowers expenses or stopgap measures like pumping,levees and raising houses

More infltrated and stored water onsite helps increase fre suppression capacity and deensible space

Retaining soil keeps land productivity high, lowering ertilizer costs


3/8

Implementation

This Conservation Strategy provides an overview o major elements in stormwater management com-mon to all land uses, ollowed by land uses o special concern. Tools and resources are provided orurther research.

What is stormwater?

Stormwater is water owing on land suraces during or within 24 hours o a precipitation event that isnot infltrated into the soil. Historically it has been viewed as a problem primarily o urban areas to besolved by the outmoded engineering practice o pave it and pipe it. Thismethod ails to properly manage stormwater in the uplands, with disastrousconsequenceslarge, powerul volumes o water, moving too ast, resulting insevere erosion and ooding in low-lying areas. This excessive runo requiresexpensive engineered systems that simply move the problem downstream un-til the runo enters a stream and ultimately the ocean, leaving the ecosystemto absorb the excess volume and pollution. This paradigm creates a cascade onegative eects.

According to a comprehensive study done in 1997, Streams with increasingimperviousness exhibit many o the ollowing conditions: increased oodpeaks, lower stream ow during dry conditions, degradation in stream habitatstructure, increased stream bank and channel erosion, ragmentation o ripar-ian orest cover, and decline in fsh habitat quality. (Kauman, Brant)

Instead o a problem, water can more accurately be viewed as an enormouslyvaluable resource to be sequestered and re-used whenever possible, and romthis perspective, it makes good sense to keep it around. Slowing, spreadingand sinking stormwater as high in the uplands as possible will ensure that anywater discharged rom hardscapes will be clean and moving slowly enough to avoid erosion and sedi-mentation problems.

The trouble with impervious surfaces

It is important to note that,h in the context o stormwater management, the phrase impervious suracesreers to a gradient o impermeability. This is expressed as a percentage o impermeability relative to theoriginal, pre-human-use condition.

Virtually all suraces modifed or human use lose permeability, and the current perception o impervioussuraces as exclusively concrete, asphalt and roofng (100%) ails to address the total impact o reducedpermeability. Many rural land uses such as poorly designed and maintained roads, subsurace drainedhillside vineyards, overgrazing and excessive discing, while only partially impervious, tend to encompassa much larger total surace area resulting in stream ow variance, ooding and erosion that can be moresevere even than urban areas.

Even small increases in impervious suraces have a disproportionately large impact on watershed health.A study in Washington ound that fsh habitat quality and channel stability both deteriorate rapidly aterwatershed cover increases to 10% imperviousness (Booth, 1991), while Maryland ound that brown troutabundance declined sharply at 10-15% (Galli, 1993).


4/8

Lost permeability prevents rain infltration and creates higher volumes o runo and greater watervelocity, which:

Cause topsoil loss, sedimentation and downcutting o watercourses

Exacerbate ooding

Reduce groundwater recharging rates Decrease stream base ow during dry months

Increased wet season ow rates also worsen pollution. Water moving aster in larger volumes will be car-rying a higher sediment load as well as more o the pollutants accumulated rom roads, lawns, vehicles,arms, vineyards, ranches and all other human uses. When these contaminants become waterborne theyseriously impair watershed health. Decreased stream base ow during dry months concentrates pollut-ants and disconnects pools, dramatically increasing mortality or all aquatic lie.

Performing a site assessment

To fnd out i your current stormwater management practices are successul, begin by perorming a site

assessment. Make it as comprehensive as possible, and remember that a walk in the rain is the best wayto get good inormation.

1. Walk the perimeter o all impervious suracesa road, parking area, roo, patio, stable, pasture, orother modifed surace. The suraces themselves are not necessarily problems eitheroten the dan-gerous part is the drainpipe, culvert, ditch or other drainage structure where the water concentratedby the impervious surace gains volume and speed.

2. Find out whether the water that comes o these suraces leaves your property.

3. I it leaves the property, fnd all the locations where stormwater exiting your property enters a naturalwaterwaya stream, river, wetlands, lake, or the ocean.

Having ollowed all the water leaving your property, answer the ollowing questions:

Where this runo daylights (leaves a drainpipe or other subsurace drainage structure), do you seerecent erosion scars or obvious resh soil being removed?

I causing erosion, is this runo also carrying sediment to a natural body o water?

Has this stormwater been running through manures, soils that have been exposed to or treated withchemicals, or other contaminated sites on your property?

Have you seen or do you have reason to believe that the water has been exposed to any kind o con-taminant upstream o your property?

I you answered yes to any o these questions, you will beneft rom implementing updated stormwatermanagement practices.

Strategies for stormwater management

With acute sediment delivery, all that can be done initially is to keep the water clean. Sediment controlsare the frst step, and will at least keep the erosion products rom reaching a natural waterway, but theydo nothing about the actual erosion problem.

Sediment ences are sturdy, permeable abric barriers that can be rapidly staked out in the path o anuncontained ow to catch soil.

Straw bales packed tightly end to end will act as a sediment ence and keep erosion product romreaching a stream, but degrade over time.


5/8

Straw wattles act like straw bales, but are lighter and more suitable or small-scale control.

Erosion controls will help retain valuable topsoil and buy time to trace the source o the problem up-stream. While stabilizing the headcut (the actively eroding upper edge o the gully) at the erosion sitemay alleviate some erosion problems, it will not address the act that the system is receiving too muchwater.

For concentrated outows, start by placing energy dissipators to break up the orce o the water andprotect the banks rom urther collapse. Depending on ow volume, you can use large rocks, brushcheck dams (a small dam constructed in a gully to stabilize the grade or control headcutting), orhand-place thick mats o brush at the headcut and bed o the gully down-stream. These woody materials can be harvested through limbing and thin-ning orests as part o a uel load reduction project.

For large areas o bare soil showing rill erosion (small shallow channels no morethan a ew inches deep ound in newly exposed soils), frst select and plantan erosion control seed mix that uses native, non-invasive plants. Then mulchwith straw to keep birds rom eating the seeds, or use erosion control blan-ketsbiodegradable woven textiles that keep soil in place and help plantsget established. Do not use plastic netting productsthey can trap and killwildlie

There are many dierent strategies available or both sediment and erosioncontrola testament to the ever growing need. For an excellent guide, readGroundwork: A Handbook for Small Scale Erosion Control in Coastal California, availableonline at http://www.mcstoppp.org/acrobat/groundwork.pd

Contact your local supplier o erosion and sediment control products or inormationon current tools and reputable local contractors.

Permanent stormwater management solutions are by ar the preerred method because they stop prob-lems beore they start. Using source control strategies means working as ar upstream as possible to slowdown stormwater, spread the water out on the landscape, and sink it into the soil to avoid excess runo.These decentralized stormwater techniques are eective because:

Dealing with the source o the problem means you only have small amounts o water to manage, andthe scale and expense o the actions you need to take are proportionately smaller but have greaterimpact

Increasing the requency o energy/ow dispersion provides many small opportunities to infltratewater that would otherwise become runo

At the community level the ideal is to disconnect those land uses with decreased permeability romdirect discharge/drainage to the stream network as completely as possible.

The ollowing eective, long-term stormwater management or low impact development strategies haveproven track records, and are detailed in the reerences available in the Tools section below:

RoowaterHarvestingcaptures rain and retains it onsite to prevent runo entirely. See our RoowaterHarvesting Strategy or more inormation.

ContourInfltrationTrenches are shallow trenches dug on contour that catch, temporarily hold andinfltrate runo and, when ull, direct water to an appropriate catchment or overow area.


6/8

RainGardens are excavated and planted depressions designed to thrive on the high volumes o wa-ter and nutrients in stormwater runo while slowing down the water and soaking it into the soil.

Bio-Swales are gently draining, o-contour channels that are heavily planted to improve water qualityprior to discharge.

GroundCovers such as mulch, gravel, or vegetation keep soil in place and trap water, giving it time toinfltrate.

Mycofltration is a strategy that uses ungus to break down nutrients, chemicals and other pathogenssuch ecal coliorm bacteria that harm waterways. Paul Stamets bookMycelium Running is thedefnitive guide to all uses o ungus.

PerviousHardscapes (grass pavers, porous concrete, etc.) allow water to seepinto the ground naturally, while retaining useul hard suraces.

EnlistyourupstreamneighborSometimes a riendly chat can move yourideas upstream and make them more eective. Try giving them this guide andoering a helping hand, or oer them a tour ater installing your own mea-sures.

Specic site challenges

No one strategy is right or all locations, so consider the ollowing beore beginningany new stormwater management measures.

Steep slopes and landslide areas are inherently unstable, so avoid directing orinfltrating runo at them, and be sure all drainage systems end well awayrom them. Landslide zones are too dangerous to modiy without proessionalconsultation, and can put others at risk. Proceed with caution.

In low-lying areas and oodplains where infltration is not possible, increasing the available suracearea o bio-fltration will at least clean up the water beore it leaves your property and help as part o

ood control management downstream.

Coastal blus are highly sensitive to erosion, and require considerable planning or successul sitedrainage.

Land uses of special concern

For the purposes o this Conservation Strategy, commercial logging operations, dairies, construction sitesand vineyards will not be discussed. Please reer to proessionals and authorities or help with these landuses as needed.

Regulations and PermittingBeore starting any work, research existing plicies or ordinances that regulate land use and stormwater.Checking with your county resource management or planning department is a good place to start.

Roads

I you do only one thing, work with your roads. Nothing impairs the natural drainage and infltrationunctions o a watershed more than roads. Without exception, more roads mean more degraded naturalstream networks. By acting as a network o artifcial streams, all owing dramatically aster and carrying


7/8

much higher sediment loads than natural streams, roads create excessive water volume that worsenserosion, sedimentation and downcutting o stream beds. For the complete manual on roads, seeHandbook for Forest And Ranch Roads, by William E. Weaver & Danny K. Hagans.

Animal HusbandryThis includes small-scale animal operations rom goats, chickens and a ew horses to larger scale eques-trian acilities, commercial dairies and livestock grazing operations. When improperly managed, concen-tration o manures results in increased nutrient ows in streams, leading to algal blooms, low oxygenconditions (eutrophication) and fsh mortality. Good practices include:

Keep roowater and hardscape drainage rom running through all areas where manures areconcentrated, and prevent direct runo to the creek

Move manure to sae containment and composting areas that exclude stormwater

Employ riparian encing to reduce livestock loafng time in the creeks

Other strategies are available online at:www.mcstopp.org/acrobat/Horse%20Keeping%20Guide.pd

Tillage Based Agriculture

Agricultural activities account or the largest percentage o non-point source pollution in the UnitedStates. Soil erosion and runo o pesticides are the major problems (General Accounting Ofce, 1990).Regardless o scale or regulatory conditions, all intensive agricultural operations need to pay special at-tention to erosion, sedimentation and chemical runo. Some successul strategies include:

Using contour plowing, cover crops and/or no-till techniques

Maintaining vegetation in ditches to act as bioswales

Incorporating sediment basins and tailwater ponds

For more inormation, see www.agwaterstewards.org/txp/Resource-Center

Rural Residential Wastewater Systems

Improperly maintained or aged and ailing septic tanks and leach felds can become sources o signif-cant nutrient and ecal coliorm pollution during peak runo events.

Owners o septic systems need to test and maintain their systems annually to ensure proper unction.Wells and Septic Systems by Max and Charlotte Alth is a useul guide.

Urban Areas

Urban stormwater rom various sources (gol courses, ball felds, median strips and industrial park land-scaping) has been proven to signifcantly increase pollution in runo. Low Impact Development (LID) isa well-developed collection o strategies or urban stormwater management. More inormation on LIDdesign and maintenance practices is available rom the Bay-Friendly Landscaping Guidelines: SustainablePractices for the Landscape Professionalby Alameda County Waste Management Authority. Visit www.stopwaste.org


8/8

Tools

Web

The Center for Watershed Protection is one o the most comprehensive sources o inormation on storm-water management. See:http://www.cwp.org/Resource_Library/Better_Site_Design/index.htm

The Low Impact Development (LID) Urban Design Tools Website oers excellent design ideas or thenumerous techniques and examples o applied LID at http://www.lid-stormwater.net/

Most coastal counties now have stormwater management websites. For a list o bay area municipal web-sites, visit the Bay Area Stormwater Management Agencies Association:http://www.basmaa.org/About-BAstormwater managementAA/tabid/55/Deault.aspx

Books

One o the best guides, written in a very accessible style with many homeowner-scale examples, isSlow ItSpread It Sink It: A Homeowners Guide to Greening Stormwater Runoffby the Santa Cruz RCD.

http://www.rcdsantacruz.org/media/brochures/pd/HomeDrainageGuide.v25.pd

For the ultimate guide to managing water with earthen structures, see Rainwater Harvesting for Drylands,Volume 2: Water Harvesting Earthworks by Brad Lancaster. http://www.harvestingrainwater.com

For help with designing and installing a rain garden, read Rain Gardens: Managing Water Sustainably in the

Garden and Designed Landscapeby Nigel Dunnett and Andy Clayton, www.timberpress.org

Design for Waterby Heather Kinkade-Levario oers a suite o creative approaches and applications ostormwater management, and includes many case studies.

This conservation strategy was produced by Brock Dolman and K ate Lundquist, Occidental Arts and Ecology Centers WATER

Institute and Kevin Swit, Swit Writing, or the Salmon Creek Water Conservation Program (SCWCP). The SCWCP is a multi-year,

multi-stakeholder eort ocused on developing alternative water supply solutions that support human needs while protecting

and restoring instream ows or fsh and wildlie.

salmon creek water conservation: stormwater management

Documents