Environmental Engineering Reference
In-Depth Information
Establishment of Decision Indicators
The characterization indicators are tools to describe in a similar way the two
locations in appreciation. In order to support the (political) decision the best
methodology is to aggregate the relevant information provided by the charac-
terization indicators into decision indicators. Therefore this study commenced
for deciding to use two decision indicators, namely: (A) “Flow under flood
conditions”, and (B) “State and integrated management of surface water
resources”. The decision indicator (A) aggregates in a direct or indirect manner
the information provided through the characterization indicators 1-3. The deci-
sion indicator (B) intends to agglutinate factors related to the water quality and
uses (concerns the characterization indicators 5-7). Both were developed and
applied to the two locations
[2]
. It was then understood that the decision indica-
tor (B) was not able to distinguish, in a significant way, the two locations under
analysis. Therefore it was decided that the most relevant decision indicator
should be “Flow under flood conditions”. The assessment of the costs for envi-
ronmental mitigation measures was carried out, concerning the scope of this
indicator. A similar analysis concerned the opportunities that the new infra-
structure could represent for the local water resources management and
protection.
Comparison of the Two Locations
Tables
1
and
2
present a summary of the characterization of the seven selected
indicators for the two locations. They were based on all existing information, pro-
vided by the representants of the two project locations
[3-5]
, and field work,
including assessment of water levels and pollution sources, and measurements with
a multimetric water quality probe. Historical water quality measurements and the
characteristics of the sanitation systems, at each location, have been analyzed as
well
[6, 7]
. Other relevant information was provided by the Environment Transport
and Planning
[8]
and the river Tagus Catchment Plan
[9]
. Flood discharges for the
Ota location was calculated by FCG
[4]
.
The available information concerning the CTA was scarce, therefore simple
calculations of flood discharges have been done with the rational method (for
instance, in
[10]
). In that method the runoff coefficient C, that is, the proportion of
the total rainfall that will reach the storm drains, was estimated following the rec-
ommendations in
[11, 12]
.
Concerning the analysis of “Flow under flood conditions”, there is a large dif-
ference between the two sites, being their relative position in the watershed the
most relevant discrepancy. The geographical location of the two sites, presented in
Fig.
1
, and the variability of the precipitation are not relevant factors for distin-
guishing the cases.
