$(20$ Pts$)$ You need to develop the $100-$year hydrograph and peak flow for the analysis of a bridge in Camas County, Idaho. The drainage basin area tributary to the crossing is $47\mathrm{.}5m{i}^2$ and the time of concentration $($Tc$)$ has been determined by the velocity method at $7\mathrm{.}5$ hours. The $100-$year point rainfall amount determined at the centroid of the basin for a $1-$hour duration rainfall event is $1\mathrm{.}65-$inches. The basin characteristics are listed in the following table. An AMC II is being assumed for the analysis.

$\backslash$table$[[$Description$,$Area $($mi ${?}^1)],[\backslash$table$[[$Herbaceous $-$ mixture of grass, weeds, and low$-$growing brush,$],[$with brush the minor element., Fair, Group C$]],29\mathrm{.}5],[$Pinyon$-$juniper $-$ pinyon, juniper, or both; Fair, Group C$,13\mathrm{.}7],[$Pastureland$,$ grassland, or range; Fair, Group C$,1],[$Pastureland$,$ grassland, or range; Fair, Group D$,3\mathrm{.}3]]$

a$.$ Determine the area weighted CN value for the basin.

b$.$ Determine the runoff $Q($also referred to as effective rainfall$)$ in Inches for the $100$year, $1-$hour rainfall event using the SCS Curve Number method.

c$.$ Develop a Unit Hydrograph for the basin using the SCS Synthetic Unit Hydrograph method. $($The SCS Synthetic Unit Hydrograph ordinates are included in Excel file.$)$

d$.$ Develop the runoff hydrograph at the bridge for the $100-$year $1-$hour duration storm event and determine the peak flow for the bridge design.$(20$ Pts$)$ You need to develop the $100-$year hydrograph and peak flow for the analysis of a bridge in Camas County, Idaho. The drainage basin area tributary to the crossing is $47\mathrm{.}5m{i}^2$ and the time of concentration $($Tc$)$ has been determined by the velocity method at $7\mathrm{.}5$ hours. The $100-$year point rainfall amount determined at the centroid of the basin for a $1-$hour duration rainfall event is $1\mathrm{.}65-$inches. The basin characteristics are listed in the following table. An AMC II is being assumed for the analysis.

$\backslash$table$[[$Description$,$Area $($mi ${?}^1)],[\backslash$table$[[$Herbaceous $-$ mixture of grass, weeds, and low$-$growing brush,$],[$with brush the minor element., Fair, Group C$]],29\mathrm{.}5],[$Pinyon$-$juniper $-$ pinyon, juniper, or both; Fair, Group C$,13\mathrm{.}7],[$Pastureland$,$ grassland, or range; Fair, Group C$,1],[$Pastureland$,$ grassland, or range; Fair, Group D$,3\mathrm{.}3]]$

a$.$ Determine the area weighted CN value for the basin.

b$.$ Determine the runoff $Q($also referred to as effective rainfall$)$ in Inches for the $100$year, $1-$hour rainfall event using the SCS Curve Number method.

c$.$ Develop a Unit Hydrograph for the basin using the SCS Synthetic Unit Hydrograph method. $($The SCS Synthetic Unit Hydrograph ordinates are included in Excel file.$)$

d$.$ Develop the runoff hydrograph at the bridge for the $100-$year $1-$hour duration storm event and determine the peak flow for the bridge design.