The example study data used throughout this manual is from Muncie, Indiana. The hydrologic and hydraulic modeling were built around the White River in Muncie, Indiana in order to make use of a the HEC-RAS Muncie example model. The modeling is not detailed, nor calibrated. The structure inventory was sourced from the National Structure Inventory. The modeling and all example data are not meant to be used in any decision making. A downloadable package of the example data is provided here. The data can be downloaded by clicking the link below. All spatial data sets are in the EPSG: 2965 (NAD83 / Indiana East) coordinate reference system. 

MuncieFinal.zip 

Terrain

The Muncie terrain is the same file used by the hydraulic engineers in modeling the existing condition hydraulics. The units of measurement are in feet. The terrain data is used in combination with the hydraulic data to determine flood depths throughout the study area. 

Impact Area Set

The impact area set consists of two impact areas: Left Bank and Right Bank. HEC-FDA requires the the entire study area to be covered by the impact areas and will not compute damages to structures outside the impact areas.

Hydraulics

The hydraulic modeling was developed in steady-state condition. The native output files have been provided for use within HEC-FDA. Depth grids were provided for exploratory purposes only. The HEC-RAS modeling for the without-project 2% annual exceedance probability (AEP) event is illustrated in the image below. The hydraulic data is used to determine estimates of flood depths on structures, and therefore the estimates of economic damages.

Flow-Frequency

The log-Pearson type 3 (LPIII or LP3) distribution parameters are below for the without-project condition. The period of record is 48 years. These parameters determine the discharge-frequency relationship, and when combined with the stage-discharge function, can be used to associate stage with AEP.

Stage-Discharge

Without-project Condition

This stage-discharge function represents the relationship (triangular distribution) between stage and discharge for the without-project condition. This data will be provided by the hydraulic engineer. In combination with the discharge-frequency relationship, this data allows for association of stage with AEP which is ultimately used to calculate damage-frequency.

With-Project Condition (Levee)

The stage-discharge function below represents the relationship (triangular distribution) between stage and discharge for the with-levee condition. Observe that some stages are higher for a given discharge (e.g. 700 cfs) than in the without-project condition. 

Regulated-Unregulated

This regulated-unregulated transform function represents the attenuation (reduction in force) of flashy flows provided by the modeled detention basin in the with-project condition that would be located just upstream of the impact area set. For some levels of inflow, outflow will be transformed to reflect the impact of the detention basin and ultimately change the estimates of economic damages from that of the without-project condition.

Levees

This system response function is tied to a modeled levee in the with-project condition that is proposed for the left-bank with a top elevation of 942 feet. The system response function, sometimes called a fragility curve in the context of levees, assigns an estimate of probability of failure for various stages of loading on the levee. From the toe of the levee at elevation 935.21 to the top of levee at elevation 942, the probability of failure is between 0 and 1. 

Occupancy Types

The Muncie occupancy types are the typical occupancy types referenced in the National Structure Inventory, and are provided with the study data as a tab-delimited file. The occupancy types include the range of structure uses, such as residential or commercial, and the associated relationships between depth of flooding resulting from the H&H relationships and expected percent damage to the structure and its contents.

Structure Inventories

Four structure inventories are provided: the base year without-project inventory, the future year without-project inventory, the base year with-project inventory, and the future year with-project inventory. In the with-project condition, nonstructural measures have been applied to 26 of the residential structures which have been elevated by 8 feet by increasing the foundation height by 8. In the future year, the number of commercial structures has been doubled to reflect an economic forecast suggesting significant growth in the concentration of commercial activity in Muncie, in between the base and most likely future years. The structures and their contents are the primary drivers of economic damages in the study area.

Compute Data Requirements

This section details the data required to compute stage-damage functions and scenarios for various project conditions and analysis years. 

Stage-Damage Functions

Four sets of stage-damage functions can be computed - two sets (base and future year) for the without-project condition and two sets for the with-project conditions. 

Scenarios

There are multiple scenarios with different combinations of flood risk management measures. Notice that for several with-project plans, existing conditions modeling is being used. We'll use without-project conditions for some of the summary relationships for with-project conditions when the with-project conditions do not affect the parametrization of those summary relationships. For example, a detention basin alone does not change the level of damage for a given stage as compared to the without-project condition and so we can use the without-project stage-damage functions for the with-detention plan.