exploring the concept of buffer zones small [compatibility mode

8/2/2019 Exploring the Concept of Buffer Zones Small [Compatibility Mode

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The reason for presenting this paper today is to vent my frustration. I was asked by a client toadvise on a way of managing wetlands on a property that was being considered for a multiple usedevelopment, shopping complex, housing, business sites etc. The wetlands on the site were

classified asFloodplainhillslope seepage feeding a watercourse, channelled valley bottom wetland, floodplain andriparian zone. We had had experienced in this particular area before where we had, because oflack of experience in this particular set of geological formations misinterpreted the hydrologyresponsible for the expression of the wetlands on the site. This was only revealed when the sitewas opened to the contractors. The soils on this site were derived from diabase, and were thusstructured, Tukulu, Sepane, Arcadia/Rensburg soil forms. The water in this landscape exists inthe subsurface and moves through the landscape at between 1.5 and 2m. Anyway on this newsite when asked to develop a wetland management plan and based on our experience with theprevious site, we attempted to, develop what we considered was a rational plan, recognizing thatduring the development process much of the soil on the site would be removed and have to bereplaced to provide effective founding conditions. During this process the water in the landscapewould be intercepted and diverted by the services, all outside of the designated wetland areas. Asa consequence we were of the opinion that some of the wetlands on the site would be lost, whileothers such as the floodplain would gain water as the water intercepted by the services would beday lighted on the floodplain. As a consequence of this we developed a reasonably complex watermanagement system in order to cater for the water intercepted in the services as well as that thatwould enter the site as rainfall. On submission of this report for comment to the localenvironmental management authority we were told that they were not interested in reading thereport and the rules were apply a 50m buffer as that would protect the wetlands.

In this particular case, the application of a 50 m or even a 100m buffer was in our opinion wouldafford any level of protection to the wetlands as the water that was responsible for their presencewas likely to have been diverted (in areas outside of the designated wetland) as well as that whichfell on the infrastructure would have runoff characteristics very different from the pre developmentlandscape


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Soils see Schulze 1985. Hydrological characteristics and properties of SouthernAfrica 1: Runoff response Water SA 11, 3: 121-128.

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What is evident in this slide is the variation in bot h drainage density and patternsof drainage. This correlates with the principle geoogical formations found in the

area, see next slide

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Diskin, M H and Green, DRA. 1985. A case of delayed subsurface flow in anurban catchment. Water SA, 11, 3: 137- 148.

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The WRC Commission is supporting a non solicited research project that aims toprovide guidance to determining the width of buffer zones around wetlands. The

definition of a buffer zone that has been proposed as a working definition isreproduced on the slide.


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The purpose of buffer zones as synthesized from the literature is to reduceimpacts of adjacent landuses on water resource quality, sustaining or improving

the ability of the water resource to provide goods and services to society andproviding protection of and providing habitat for aquatic and semi aquatic species


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This is achieved by maintaining an environment that facilitates, sedimentremoval, nutrient removal, controlling the local microclimate, providing habitat for

wildlife, screening of adjacent disturbances, creating linkages between habitats,improving channel stability, create opportunities for groundwater recharge andaesthetic appeal.

Regulating the hydrology is not explicitly addressed although it could be inferredfrom the fact that sediments are removed that the hydrology is influenced bybuffer zones.


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I am now going to run through three sites where there is am impending change inlanduse. As I go through these slides I would like you to assess whether the

application of a buffer zone will contribute in anyway to the protection of the waterresource, in this instance the wetland.


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Erosion through a wetland as a consequence of development in the catchment: .Nelspruit , geology primarily granites.


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Erosion of a wetland downstream of a housing estate and national road, R28/R55 intersection on Granites

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Proposed changes in land use on Granites showing the extent of the wetlands. A50m buffer zone was advocated by wetland specialists to protect them from the

impacts of development.


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Control points in the way of exposed unweathered granites behind whichsediments could accumulate and which effectively reduce velocities/store water.

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Based on some simple calculations, the deeper soils on the site > 1.0m in depthcan store the equivalent of about 3900m3/ha. The deep soils are the sources of

water that keep the wetlands alive during the dry season

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The placement of infrastructure on these non wetland soils will have a significantimpact on the rainfall runoff characteristics, particularly as a consequence of the

interception of rainfall, its collection in a storm water management system and itssubsequent discharge into the environment as point discharges.

The wetlands at the bottom of the site will erode if the 50m buffer is the onlymeasure applied to protect them.

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A site on the Mpumalanga highveld supporting wetlands .

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Development on the non wetland areas required that groundwater be interceptedto protect foundations. This was the primary source of water for the wetlands

downstream of the site. A 50m buffer around the wetlands will do nothing toprotect them as their source of water has been inexorably altered.

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A mining site, where a 100m buffer is advocated by most environmentalists andwetland scientists to protect areas of sensitivity and wetlands


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A typical mining site on the highveld showing complete removal of aquicludes andother structures that regulate horizontal and vertical flow through the regolith.

Any wetland downslope of this site will have its supply of water altered.

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The area proposed for open cast and the wetland, if the catchments or portionsof the catchments supporting wetlands are altered by open cast mining, then the

wetlands are likely to disappear, and the application of a 100m buffer is unlikelyto result in their salvation.


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A Vector diagram that was used to define catchments and connectivity betweennon wetland and wetland areas

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If the intention is to protect a wetland itself or the biodiversity associated with theecotone between wetland and dryland, the concept of a buffer should extend to

include not only a physical measurement, but also to the management of thewater supporting the wetland. Should the volumes, periodicity of flow, quality orthe manner in which the water reaches the wetland change it is unlikely that thewetland will continue to exist in its current state, and hence the application oflinear buffer is unlikely to achieve the intention of protecting either the wetland orthe biodiversity associated with the wetland and is associated ecotone

The recommendation to provide a 15m buffer, as recommended in a guidelinedocument prepared by Kotze et al is in our opinion an administrativeconvenience and fails to take into cognisance the hydrological complexities ofwetlands as well as the influence of local geology and soils on the extent and

maintenance requirements of wetlands. We thus consider that a moreappropriate means of buffering wetlands is to ensure that the hydrology isresponsibly managed, and that the buffer includes a range of interventions toensure the future of the wetland, as well as any ecotone that might be required.The width of the ecotone in this event should be determined by identifying itsfuture purpose or role.


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We suggest that the primary function of a buffer should be to afford protection tothe wetland from changes in hydrology associated with changes in landuse, ie

manage the hydrology first. Once the wetland has been afforded a degree ofprotection only then should consideration be given to deciding whether a bufferzone is required or not. Based on the above selected examples, the changes inhydrology and associated water quality changes have a significant impact on thewetlands associated with these changes. This is not surprising given thatwetlands and the types of wetlands in a landscape reflections of the hydrologicalprocesses in the particular landscape setting. As landuse changes so do thewetlands as the adjust to the imposed hydrology.

For this reason we would advocate that in order to comply with the intentions of

the Water Act, that the primary role of a buffer should be to afford protection tothe wetland, .


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exploring the concept of buffer zones small [compatibility mode

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