Hydrological and hydraulic surveys for photovoltaic plants.

The objective of a hydrological survey is to define flood magnitude for given return periods. As part of the hydrological survey, hydraulic calculations are made with the aim of establishing the levels and velocity of water flowing within the plot or site in question and coming up with a pre-design of a drainage system which can cope with possible flooding during the return periods considered.

During the initial phase, calculations are made, and the relevant hydrological and hydraulic models are generated in accordance with the available basic data.

In the event of subsequent earthworks resulting in a modification of the topography which was used to generate the models during the first phase, we would undertake to produce a new flood model during the second phase using the new topography arising from said earthworks. We collect the following data during the first phase:

Historical data relating to precipitation, hydrographic basin (drainage basin) and gathering flood-risk data

Compiling, evaluating, and preparing topographical, hydrological, land use, geological, and meteorological (rainfall) data which is publicly accessible.
Collecting historical flood data about the area which is the object of the survey.
Identifying possible flood risks or problems (which events are relevant, and which are not) due to rainstorms and main local rivers.

GMS Internacional can gather information from IDF curves for its calculations. In the absence of this information, it also feasible to provide this data by using other sources, such as adjacent fields of research or making assumptions based on experience. All possible discharge points for estimated rainwater within the drainage system and its discharge area will be identified and agreed with the client. We can estimate the maximum flow for these discharge points based on different equations normally used for the design of rainwater drainage systems or small basins.

This research gives us the maximum flow for each predefined discharge point for the duration of the precipitations and for the required return periods (for example, 25 and 100 years).

Hydraulic modelling and flood risk assessment

Following these phases, we then carry out analysis to manage water flow within the plot or site which is the object of the assessment; calculations are made using basic available data and by using the American Rational Method, Triangular Unit Hydrograph, Ven Te Chow and SCS.

We will then use models based on the programs ArcGIS, HEC-Ras, HEC-RAS 2D, and eventually HEC-HMS (SCS), by which we calculate the maximum flow, the extent of the flood surface, and the resulting water levels and velocity on the area (topography). Flood maps are generated for different return periods. The water surface can be identified by intersecting it with the MDT model.