Saving the Springs: Urban Expansion and Water Quality in Austin - Politics of Urban Runoff: Nature, Technology, and the Sustainable City - page 55

going to be maintained and they wouldn't work. So that's why you do
impervious cover limits on top of nondegradation.” 83
Impervious cover limits are an easily understandable regulatory re-
quirement that ensure equitable application of environmental protection
to all properties in the Barton Springs Zone, but they are also scientifi -
cally controversial. The impervious cover limits were reportedly derived
from environmental thresholds established by Tom Schueler at the Center
for Watershed Protection in Ellicott City, Maryland. Schueler, an early
proponent of Low Impact Development and source control methods for
stormwater management, developed these thresholds from research data
on urbanizing creeks in the Pacifi c Northwest. The authors of the SOS Or-
dinance (environmental lawyers, scientists, and engineers) used Schueler's
thresholds as scientifi c justifi cation for water quality, despite the com-
pletely different hydrologic and geologic conditions of the Hill Country.
Thus, seemingly universal scientifi c fi ndings were applied to particular
local conditions. Moreover, some scientists question the ability of the im-
pervious cover thresholds to refl ect the complexities of stormwater runoff
and aquifer fl ow patterns. A local geologist notes:
The public is only smart enough to understand the link between impervious cover
and water quality but this approach is not nuanced enough to refl ect how the
aquifer functions. We could make a substantive impact by protecting the aquifer's
most vulnerable features but this doesn't fi t with the legal system where property
rights are dispersed. If we could do a regional survey and protect the most sensitive
features, we could do a lot more than impervious cover limits. This would allow
for development while also protecting the aquifer. 84
In other words, the problem with impervious cover limits is that the ap-
proach treats all properties equally, but the landscape is heterogeneous
and includes varying areas of sensitivity that are not evenly distributed.
The parcel-by-parcel application of land use restrictions is a topo-
graphic approach to environmental regulation and is in direct confl ict
with the complex topologic relations of the Hill Country landscape and the
underlying Edwards Aquifer. There is a fundamental mismatch between
the social system of segmented property ownership and the physical sys-
tem of landscape connectivity. Refl ecting on this clash, an environmental
activist involved in the drafting of the SOS Ordinance agrees that “it
really is fairer to property owners when it's not as scientifi cally exact
or nuanced.” 85 The impervious cover limits effectively call for large-lot
residential development on upland surfaces and moderate hill slopes, but
it is unclear if this type of development, even if it strictly adheres to the
SOS Ordinance requirements, will protect downstream water quality. 86